Fixes #196. If a charset is already specified in the content-type, I opted to leave it there. Else, no charset will be added to the content-type line when the the effective content-type is JSON.
I also reworked the content-type-checking condition make it more legible.
Don't add a charset if none is specified and the content-type is JSON.
Merge '#197' of quantum-omega into bugfix/nocharset
@bertjwregeer -- this is a bit of a shot in the dark, I think, but I am wondering if you might be willing to add some context to an Open edX component PR related to this particular webob change.
@mattdrayer Yep, with pleasure. Will update whatsnew-1.6 to further clarify why we removed it.
Awesome, thanks much!