More testing, new failing test for JsonWithDeepLinks

Better performance test harness for IMediaTypeHandlers

Fix mediaTypeHandler tests to use .Write<IEnumerable<X>>() where we would expect IOutput<IEnumerable<X>>

LinkConverter now doesn't barf when passed an IEnumerable<> interface directly.

JsonWithDeepLinnks, links in the entire hierarchy still do not work.

ExplicitTestConverters will write full graph now, on par with other converters
Merge pull request #78 from EddieGarmon/feature-MoreBetterTesting

More testing, new failing test for JsonWithDeepLinks