Css refactor

[nlhkabu]

Major CSS refactor moving codebase over to BEM naming convention. Cleaned up components and added documentation.

[nlhkabu]

html-linter is throwing linter errors because of the new BEM naming convention.
It does not look immediately obvious to me how to get around this :(

[dstufft]

We can probably just make html linting to shut up about that particular kind of error.

[nlhkabu]

@dstufft - FYI we will need to merge this PR on pypi-theme https://github.com/python/pypi-theme/pull/2 at the same time, so that the HTML/CSS remains in sync.

[dstufft]

@nlhkabu pypi-theme doesn't auto deploy, so the easiest thing to do will be to merge that PR, then I'll make a release of pypi-theme and this PR can be updated to change the pypi-theme version.

[dstufft]

By the way, I think you can tell html_linter.py to shut about about this by adding names to the disabled list in the Makefile#L118.

[nlhkabu]

By the way, I think you can tell html_linter.py to shut about about this by adding names to the disabled list in the Makefile#L118.

aha! Thank-you :)

I just added a few more things to my todo list on this PR (see #813 (comment)), but hopefully we can get it merged in the next few days :)

[nlhkabu]

ok @dstufft this is ready to merge with a new release of pypi-theme :)

Closes #813