chore: configure Travis with placeholders to run Karma tests in Firefox
chore: replace gulp-karma with karma API

Reduces config duplication and need to manually handle errors
chore: set travis to skip_cleanup

If you decide to build on Travis instead of locally committing builds to git this will ensure they don't get cleaned
chore: updated npm packages
chore: updated travis yml file info
Merge pull request #24 from ocombe/pr/23

feat: add travis CI

Closes #23