chore(test): add `--watch` flag to `gulp test`

CHANGES
- if `gulp test` is run with the `--watch` flag, karma will keep the
server open and rerun all tests on file changes
test(ajax): add jasmine-ajax mock
chore(jshint): add jasmine globals
chore(karma): add wildcards to file strings

CHANGES
- now all files in the `js/` directory that end with `.js` will be
compiled
- now all files in the `test/unit/` directory that end with `.unit.js`
will be compiled
- now all files in the `test/unit/mock/` directory that end with `.js`
will be included
feature(Http): add Http utility module