Bug 2965: enable Coveralls
update README to markdown, with coveralls/travis links
Display the build number instead of the buildid in the waterfall.

This is more consistent with eight. Beside, the buildid is an internal reference that doesn't need to be communicated to the user.
actually run coverage in travis
Use an SVG badge for coverage
README.md -> README.rst
Merge benallard/buildbot:patch-1 (PR #1290)
Merge djmitche/buildbot:bug2965 (PR #1293)