Adds lift-json-scalaz7 (Scalaz 7 support).

Adds lift-json-scalaz7 (Scalaz 7 support).
* Adds a new submodule for lift-json-scalaz7.
* Maintains lift-json-scalaz for Scalaz 6 support.
* Updated json-scalaz directory structure from lifweb to liftweb.
* Updated README to correspond to Scalaz 7.

Discussion on Lift mailing [list](https://groups.google.com/forum/?fromgroups=#!topic/liftweb/dTIF044jAww).