Significantly reduced the size of the final gem file.

The resultant gem file for `aws-sdk-core` was previously
about 800k. It now builds to 214k. The following changes
have been made:

* Removed all unecessary runtime files from the gem:
  * unit test files & fixtures
  * integration tests
  * doc src

* Now minifying the API models
  * removing whitespace
  * removing doc traits

The removal of doc traits accounts for the largest
savings. Removing whitespace from the API JSON models
is also significant.