Update translate.js

Added that use method returns promise object
Update translate.js
Load fallbackLanguage

separate load and uses. Load fallbackLanguage if needed
Add tests
Use angular.isFunction
Throw error if no key is specified
Throwing test

Expect load() to throw an error if no language key is specified
Add some tests

test that we can load languages without using them and that
fallbackLanguage and preferredLanguage are automatically loaded
Test fallbackLanguage
Change deferred arg on load

Change ```$uses``` for ```key``` since we are not using the language
anymore
tests(midway): adds some midway testing
update version
Update README.md
fix(tests): travis CI
Load fallbackLanguage

separate load and uses. Load fallbackLanguage if needed
Add tests
Use angular.isFunction
Throw error if no key is specified
Throwing test

Expect load() to throw an error if no language key is specified
Add some tests

test that we can load languages without using them and that
fallbackLanguage and preferredLanguage are automatically loaded