Added coverage configuration file and make targets.
make clean will also remove coverage datafile.
First attempt at using coveralls with Travis.
First try at adding badge with coverage results.
Removed trailing blank line.
Adjusted coverage to make more sense on Travis.
Added apt-get update to ensure repo index is up to date.
Small style tweak to .travis.yml.

... for consistency.
Merge pull request #125 from enthought/test-coverage

Added coverage for test suite.