Display minimal complete definitions for type classes

This corresponds to the new {-# MINIMAL #-} pragma present in GHC 7.8+.
I also cleaned up some of the places in which ExportDecl is used to make
adding fields easier in the future.

Lots of test cases have been updated since they now render with
minimality information.
Strip links from recently added html tests

These were accidentally left there when the tests were originally added
Bump version to 2.14.1 and update changelog