Put back in some older code to save source_code property.
Add helper method for typing in CodeMirror, make it robust to Mac and Unix.
Added info to changelog for recent pull requests.
Added comment regarding the fact that the temporary bug fix should be eventually removed.
fixing segment io settings bug

* Moving to the auth tokens section
* Removing the feature flag logic since all features are loaded earlier
```
    for feature, value in ENV_TOKENS.get('MITX_FEATURES', {}).items():
        MITX_FEATURES[feature] = value
```
moving settings into the auth tokens section
Merge pull request #180 from edx/jarv/fix-segment-io

fixing segment io settings bug
Merge pull request #179 from edx/valera/additional_comments_on_youtube_api_bug

Addtional comments for YouTube API bug.
Merge pull request #178 from edx/valera/adding_changeleog_info

Added info to changelog for recent pull requests.
switch to using environment variables to get key for Segment.io
add new collection configuration to support a 'trashcan' for assets. Update class factory to allow callers to specify if they want the default set of assets or the trashcan
add ajax callback entry point to remove the asset
fix sizing of the delete column
add CHANGELOG entry for work
update warning message
add unit tests for asset delete/restore
use the new notification tools for the confirmation dialog
remove invalid comments
forgot to internationalize one string
put back the verbose switch in xml_importer.py