Enable MIMA
Version to 2.3.0-SNAPSHOT

Since I'm adding features
Add more flexible content-type handling for JSON in http client responses

Deprecates asX methods, adds new "x" (and "x3" for rojoma-json 3) methods
which accept a predicate to determine whether the content-type is
acceptable.  Defaults to requiring "application/json" but includes values
for accepting geojson (as either "application/json" or "application/vnd.geo+json")
or text/plain.

Also corrects the names of classes in @throws sections of Response's
scaladoc.  They were accurate back in the v1 days but haven't been
since then.
binary compat fixups
Merge branch 'flexible-json-responses'
Setting version to 2.3.0
Setting version to 2.3.1-SNAPSHOT