Compatability commit, require json <= 1.7.5, bump to rjr version 0.16.3
Implement workaround for latest versions of compatability gem

Implements second workaround from https://github.com/flori/json/issues/179
so that json module doesn't have to be monkey patched.

Hopefully https://github.com/flori/json/pull/182 will be accepted and a
more efficient solution may be implemented
bump version to 0.16.4