Remove Module::Install::ProvidesClass, setup provides manually ourselves.

Remove Module::Install::ProvidesClass, setup provides manually ourselves.

Module::Install::ProvidesClass just doesn't work for us - it still doesn't
know about roles, doesn't find all of our classes (not even all the MXD ones)
that PAUSE won't find itself, and also won't currently install cleanly from
CPAN.

The alternate solution here is _totally totally mental_, but appears more
reliable than PPI and all that jazz. It's also significantly faster:
Just loading the entire of Gitalist is waaay quicker than parsing it
all with PPI.