Allow XBlocks to be used with django 1.6
Allow XBlocks to be used with django 1.6

4eek/XBlock,lovehhf/XBlock,edx-solutions/XBlock,EDUlib/XBlock,nagyistoce/edx-XBlock,open-craft/XBlock,EDUlib/XBlock,lovehhf/XBlock,edx-solutions/XBlock,edx/XBlock,edx/XBlock,nagyistoce/edx-XBlock,4eek/XBlock,mitodl/XBlock,mitodl/XBlock,open-craft/XBlock