Include scripts that call goog.addDependency

According to the Closure Library [FAQ](https://code.google.com/p/closure-library/wiki/FrequentlyAskedQuestions#When_I_compile_with_type-checking_on,_I_get_warnings_about_) `goog/deps.js` should be included even though it cannot be `goog.require`d.

This change forces the inclusion of any scripts that call `goog.addDependency` but don't otherwise `goog.provide` anything that is `goog.require`d elsewhere.

Fixes #15.