chore(package.json): update traceur-compiler to v0.0.45

Karma was having issues with the older release
chore(karma.conf.js): slight adjustments to files loaded and preprocessed

These adjustments match working patterns from watchtower.js and other v2 repos, and are
working in my local tests.
chore(gulpfile.js): add task for running tests (`gulp test`)

It's more fun to just say "gulp test" instead of the whole "karma start <config> ..." thing.

Closes #17