Make jig a dependency

Provided there's a config somewhere in the classpath, this means
a `lein repl` in the repo will understand `(go)`.
Clarify the set up of jig

In particular, add a note on using jig from the azondi directory, and
make it obvious that the `.jig` directory is in the user's home
directory.
Use the Jig REPL prompt
Actually I don't know this is correct
Merge pull request #16 from squaremo/jig_as_dep

Let the jig REPL be run from the azondi directory