Add coverage and coveralls support to the test runner.

 * FIXES the coverage part of #9865.
Fix Python2.6 CI failures due to changed twisted.trial.unittest.TestCase API.
Fix another CI failure due to twisted.trial API changes in Python2.6.
Add sitecustomize.py for running parallelized coverage tests.
Add integration tests which start the BridgeDB servers through the cli scripts.
Add unittests for the bridgedb.crypto module.
I *really* hate Python2.6.

The argparse module wasn't a builtin in Python2.6, so we have to add it to
requirements.txt otherwise the CI builds fail.
Fix unittest fail for test_bridgedb due to changing where make-ssl-cert puts files.
Make the IRC Travis CI bot a bit less noisy.
Sphinxify the docstring for bridgedb.EmailServer.getGPGContext().
Refactor bridgedb.EmailServer.getGPGContext() to improve exception/error handling.
Don't include the old unittests in the calculation of coverage results.
Move method wrapper utility @fileCheckDecorator() to bridgedb.test.util.

 * ADD bridgedb.test.util, with method decorator @fileCheckDecorator, and give
   that decorator a docstring with a doctest example.
Add unittests for bridgedb.EmailServer.getGPGContext() function.
Improve error handling for the HTTPServer if a port is already occupied.
Ignore _trial_temp/ directory.
Fix unittest failures in test_EmailServer due to creating an existent dir.
Remove coverage html report generation from .travis.yml directives.
Fix dependency requirement libgpgme11-dev → libgpgme11.
Or… we need both libgpgme11 and libgpgme11-dev dependencies.