Big parser refactor

[davidfischer]

• broke the parser into a Requirement class
• refactored the unit test suite
• better handling of VCS

This is backwards incompatible in the sense that parse returns a generator of objects rather than dicts. However, the objects behave like dict-like objects. The parser is much more complete in my opinion as it handles more use cases from the revised spec. It should fix #10, #8, and #12 more or less.

I need to create more docs but here's some usage:

>>> from requirements import parse
>>> list(parse('https://github.com/django/django/tarball/stable/1.6.x'))[0].uri
'https://github.com/django/django/tarball/stable/1.6.x'
>>> list(parse('django==1.5.2'))[0].specs
[('==', '1.5.2')]
>>> list(parse('django==1.5.2'))[0].specifier
True
>>> list(parse('-e git://git.myproject.org/MyProject.git@v1.0#egg=MyProject'))[0].editable
True
>>> list(parse('-e git://git.myproject.org/MyProject.git@v1.0#egg=MyProject'))[0].revision
'v1.0'

I wouldn't mind a weigh-in by @treyhunner on this change.

[davidfischer]

Ugh. Python3.2 and it's lack of compatibility. I'll probably just drop support for it. Nobody uses 3.2 anyways.

[treyhunner]

:+1: for splitting out the code into an object that can be used more flexibly.

As for Python 3.2, I agree that most people don't use 3.2, but I think 3.2 is a pretty good guideline for "you're doing it right". In this case since all strings should be unicode, instead of prepending u to them you should put a from __future__ import unicode_literals at the top of every file.

Unrelated: you might consider sticking a Coveralls badge in the README too just to demonstrate code coverage. Example: https://github.com/treyhunner/pep438#pep438