First usable release after some heavy reworks

All issues in #53 have been resolved among many other. bookwyrm is still
considered unstable, or at least in some beta-phase; this release was
somewhat rushed just because I wanted it out the door. Here it is.

Highlights of this release are:
* improved log handling and C++-Python interfacing;
* learned --accuracy option, specifying fuzzy string match accuracy;
* adhered to the modifier passed to --year;
* display how many plugins are still running;
* fix and overhaul plugins/libgen.py;
* add a test framework with some tests - run these with ctest(1);
* overhauled Python API to only rely on dicts (more Pythonic);
* resolve mirrors only for items that the user wants to download:
    * HTTP headers can be returned and set before download;
* overhauled out-of-code documentation, and
* added a CHANGELOG.md.

Future releases will likely refer to this changelog instead of inlining
changes here.

v0.5.0: First usable release

This release constitutes the first usable release. Some limitations
apply, the greatest one probably being that Linux + GCC is the only
supported combo thus far (see #51).

This release is not considered stable; bookwyrm has now entered the
first big bug-squashing stage. All issues listed in #53 and otherwise
tagged with v0.6.0 shall be resolved before next minor release.

Highlights of this release are:
    * dropped some dependencies;
    * replaced termbox with ncurses;
    * add plugin for Library Genesis;
    * a lot of wrestling with CPython to bypass segfaults;
    * implemented downloading of items via libcurl;
    * TONS of refactoring and general improvements.

Fourth minor release

An in-development release to trump all those before that are written in
Python. Features of this release are:
    * a text user interface;
    * interfacing with Python, and
    * tons of code cleanup and restructure.

Any sources have yet to be implemented; bookwyrm is still some ways of
from a first major release.

Third Relase of First Minor, C++ rewrite

Changes since last release:
    * logging is now done to debug instead of info;
    * a lot of code cleanup;
    * improved comments;
    * allow an option to be specified more than once, which makes it
      easy to grab all the values as a vector;
    + constructor added for option groups without synopsis;
    + port item::matching() over from the python branch and
    + construct the wanted item from cli arguments.

Second release of First Minor

Changes since last release:
    + add logging via spdlog (specify -l for info-level logging), and
    + add option groups for improved --help and error reporting.

Inital C++ version

Third Minor

Bug fixes, better variable names, better code (and worse in some places
for as placeholders).

Item has been revisited again, now sporting a less ad-hoc data structure
(with even more namedtuple with optional arguments).

The source gscholar (Google Scholar) has also been added.

for a full list of changes, please see the commit range:
<https://git.dragons.rocks/bookwyrm/log/?qt=range&q=e8f84f87f9a7a4fbab52a0e7786f2b016330d6db..6c66130c9b38e24e54a9b74fe99d911e4ffd4061>

Second Minor, Alpha.1

bookwyrm now prints debug information when the --debug flag is in use

Second Minor Release

general:
    - PEP8-ify (almost) everything (see setup.cfg);
    - argparse in a dedicated function;
    - add the serie flag.

ligen:
    - become an object;
    - add extraction of {item serie,page count, file size} if any.

scihub:
    - added (only possible with --ident, as of now).

Alpha 3

What's this about?
    + It's now possible to search for multiple authors by specifying an
      extra -a flag. The two flags are inclusive.
    ~ Rework of item attributes; now using named tuples
    ~ General fixes and improvements.

What can bookwyrm do?

While all results are still printed, mirrors are no longer fetched
because it takes forever to (4 GET requests per item). Mirrors will instead
be fetched when an item has been chosen (not implemented yet).

Speaking of slow GET requests, bookwyrm now stores libgen query results
in /tmp/bookwyrm-<--title argument>.html which makes everything so much
faster.

There has been some general code cleanup: simplified statements, better
comments and varaible names, removal of superflouos code, minor bug fixes, etc.

The biggest commit in this alpha, however, is the use of fuzzy string
comparison! Item attributes which can't be matched exactly (authors,
title and publisher) are instead fuzzy compared. Thanks @seatgeek/fuzzywuzzy!

Currently known issues:
    - libgen: authors are in some cases delimited with ' and ', which
      isn't parsed for.

What can bookwyrm do?

As in the first alpha, bookwyrm will query Library Genesis with whatever
is passed with the --title flag and print whatever info she finds -- but
now she prints _all_ results.

However, she now also extracts URIs for mirrors. As of this release,
she can extract for golibgen (at the cost of one request) and for the
item's torrent (free). The torrent file is converted into a magnet link,
since we only want her to create files for items she is downloading.

Aside from that, the codebase has been refactored some for a more
general structure, and a bug where the item edition couldn't be
extracted has been fixed.

Initial version

What can bookwyrm do?
---------------------
Currently, it is only possible to pass the `title` flag.
Bookwyrm will query Library Genesis and print information about the
first item found.