Recognize arbitrary Json responses

[harti2006]

Currently the s1st parser serializes json responses with automatically: https://github.com/zalando/swagger1st/blob/183cba7e30e62da6a23df9078e7062830885d72e/src/io/sarnowski/swagger1st/parser.clj#L344

Unfortunately this happens only if the content type matches "application/json" exactly. In other words

• "application/problem+json"
• "application/json; charset=UTF-8"
• ...

are not recognized and hence not serialized.

Swagger1st should either support all possible json formats (like https://github.com/ring-clojure/ring-json) or not none at all.

[oporkka]

I think #45 and #49 are related