Update examples

Added two new examples:

1) Asynchronous API server with Couchbase backend using Goliath and
   Grape framework

2) Gzip transcoder, the demonstration of writing custom client-side
   data filters for Couchbase (in addition to three built-in:
   Document, Marshal and Plain)

Change-Id: Id35f083fe6bf33e34cb914754695e23849a78c11
Reviewed-on: http://review.couchbase.org/26153
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>