Attaching grammars directly onto client instances, fixes #74

Allows passing in an intitialized client instance to the constructor
optional callback for pool#destroy, fixes #75
Merge branch 'master' of github.com:tgriesser/knex

* 'master' of github.com:tgriesser/knex:
  Add link to @moll's homepage.
lots of docs & updated comments
release 0.4.2