Support media types which use the +json suffix

[ctuckz]

Added support for json-like media types that use the +json suffix, such as application/problem+json or application/hal+json.

• Schemas are now generated for request and response bodies when the content type includes "+json"
• A consumes section containing the content-type of the request body is added to the Swagger output
• Fixed potential issues due to casing of keys in headerKeyValues

I originally tried to handle the case where no content-type header was included along with a request body, but the change was too out of scope. #8 was created to address it.