chore(testing): add coverage reports to tests

I'd like to add coveralls support so that this test coverage can be improved today,
it would be a nice thing to do.

Closes #37
chore(grunt): don't instrument for coverage reports when --debug flag set

This just adds a helper to avoid instrumenting code and creating unreadable crap (which is not very
nice for debugging!) when the --debug flag is used in `grunt test`. It also works for regular karma
runs.
chore(gitignore): ignore /coverage directory

This directory isn't really needed in the distribution, as coverage reports will be hosted on
coveralls.io in the not too distant future.

Keep it simple for now.
chore(testing): add coveralls.io reporter for Travis-CI test runs

LCOV HTML reports should nicely show what parts of the module are being poorly tested,
and should assist in improving the robust-ness of it. At any rate, it will let me add
a nice badge to the README, so that will be nice.