Remove dependencies on closure library

[lukesandberg]

Depending on the closure library brings in a lot of code that we then have to use closure compiler to remove

In the long run we should invest in dropping these dependencies

This will require an audit but the major pieces are:

• goog.asserts, for runtime validation, we should build our own predicate functions
• gooog.crypt.base64 we should look into adding our own base64 encoding/decoding library
• goog.object/goog.array/goog.string helpers. We sohuld look into depending on modern platform features instead of these ponyfills