Remove unused travis OS dependencies.
Add coverage rcfile for travis commands.
Remove very old and unnecessary argparse dependency.

It appears to be breaking CI builds:
https://travis-ci.org/isislovecruft/bridgedb/builds/24138587
Separate coverage commands in Makefile so that .travis.yml can use them.

Because we only want the first two commands to run on TravisCI. This changes
nothing for the `make coverage` directive, it'll still function in the same
way.
Remove unused dependencies recaptcha and MarkupSafe from requirements.txt.
Switch to Makefile `coverage-test` directive in .travis.yml.
Add missing parens after call to _getRotatingFileHandler in util.
Fix problems with rotating logfile handler in newest python2.7.6.
Set a default logfile name, otherwise chowning chokes on it.
Add weird except handler for missing os.ST_WRITE in Travis.
Merge branch 'hotfix/requirements-travis' into develop