use wercker instead of travis-ci to enable full test harness

Before this commit: We use travis-ci (ubuntu vm) to run
just the unit tests. We cannot run functional tests on
travis-ci due to lack of platform support.

After this commit: Run the full dockerized test harness on
http://wercker.com to run `hacking/runtests.sh`, which runs
all the unit and functional tests on el5, el6, and f20 to
assert supportability on all the pythons 2.4 through 3.x.

A sample test run is at
https://app.wercker.com/#buildstep/5346d0054daac943370042c7

At the above link...

1. Click **run the docker test suite** in browser to show log
2. Scroll all the way through to see the verbose output and
   summary at bottom.

Note: `hacking/runtests.sh` exits non-zero if any test fails
on any of the platforms.

Wercker docs are online at http://devcenter.wercker.com/#
spec: remove dependency on GitPython

3ae15969237b8cd292fdd7601e8ed74b92971193 removed GitPython
from the source, but forgot to remove the dependency from
the rpm spec file.