Work around IE9 console.error not being bindable

Since console functions do not inherit from Function, underscore cannot
bind them, since it thinks they are plain objects...
Use JSONP on IE9 for UtfGrid requests, since IE9 doesn't support CORS

fixes #746, fixes #747
Fix settings.py TILE_HOST documentation to be accurate
Merge pull request #786 from maurizi/topic/ieFixes

IE9 fixes