tracking in idashboard should only log json-serializable objects
use unicode instead of str for casting track.views args in idashboard
Merge remote-tracking branch 'origin/release' into rc/2013-07-16
add a default XML serialization if the 'data' field is empty or None. Some XModules now - like video XModule - do not have XML set in the 'data' field
Merge pull request #420 from edx/fix/cdodge/hotfix-export-crash

[HOTFIX] add a default XML serialization if the 'data' field is empty or None. So...
Merge pull request #422 from edx/release

Hotfix: 2013-07-17