[Cython] New hosting

[Robert Bradshaw]

Since Cython's inception, we've been able to take advantage of William
Stein's and University of Washington's infrastructure for hosting the
Cython project along side that of Sage. However, due to UW policy,
those days are coming to and end. Maybe it's time--Cython has come a
long way from its birth of SageX + lxml.

So the question is where to move. Our primary needs are not that
large: we've got a site, a bugtracker (trac), and a continuous build
(jenkins) currently being served (the source code and wiki have
already been migrated to github).

I would propose that we look into moving everything we can over to
github. For starters, they now offer serving simple sites from a
repository (cython.org) so that seems an obvious choice. I know their
bug tracking v1 was considered far inferior to trac, but the situation
may be better now (at least worth exploring). We also have travis.ci,
which isn't as configurable as jenkins, but may be good enough. (The
biggest deficiency is that it probably wouldn't allow for building and
testing Sage regularly, or benchmarks, this is the one thing that we
may need to find/provide custom hosting for.)

Thoughts?