Release notes 12-16-14

@srpearce @fredsmith  @explorerleslie 

need to complete by 11:00

FYI @lamagnifica @catong 
It's not behind a feature flag - I didn't fully work with the author on the PR, Don and Andy reviewed it, I only helped at the very end once it passed all the review steps. The 10 MB limit is configurable in settings:
`cms/envs/common.py:725:MAX_ASSET_UPLOAD_FILE_SIZE_IN_MB = 10`