Add access-control-max-age header to cors middleware for avoid options pre-flight.
Merge pull request #64 from taigaio/avoid-options-pre-flight

Add access-control-max-age header to cors middleware for avoid options pre-flight
Fix bug #752: Show only description_diff in emails
Remove south related monky patch.
Comment/Remove generic tabular inlines.
Remove obsolete data from README
Remove now unused sql directory
Remove old south migrations.
Update requirements.
Remove now obsolete migrate_history django command.
Remove now obsolete migrate_references django command.
Remove obsolete code that uses reversion.
Remove reversion from requirements.txt
Register timeline signals in app.ready hook.
Fix settings compatibility.
Remove south and reversion from requirements.txt
Add django1.7 migrations.
Update development dependencies.
Add pillow to requirements.
Refactor test factories to new factoryboy version (more compatible with django 1.7)