pytest is the preferred way to write and run unit tests these days and
it has a cleaner interface - so lets switch to it. The tokenizer tests
especially are much easier to read/understand.

This was mostly done with find/replace regexes and then cleaned up
manually.

In addition to replacing the manual version check, this will also
instruct pip to download an older version of mwparserfromhell for
users running earlier Python versions rather than just getting something
broken.

Fixes #221.

To make the package build reproducibly, sort the source files in a
deterministic order instead of just globbing them.

Patch originally from
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=842628>.

* Remove unnecessary win_install.ps1.
* Add appveyor version update to release script.
* Make setup.py's pure Python fallback code less intrusive.

'setup.py test' also uses SystemExit, with args[0] as False.
Detect and re-raise.

Add support for building without extension even when compiler
is functional, and set up extension-less travis builds.

Allow the compilation of the extension to fail, and switch
to pure python mode.

Causes issues if the locale is not set to utf-8

* Removed unittest2 dependency on Python >2.6.
* Moved discover_tests.py into tests/.
* tokenizer.c: Fixed errors noted by -Wshorten-64-to-32.