RCBC-136 Build shared object for ruby 2.0
RCBC-136 Build shared object for ruby 2.0

Also fixes build script when using latest rake and rake-compiler

Change-Id: I109dd07d901c5054499ff892383613bb932a2ff9
Reviewed-on: http://review.couchbase.org/28344
Tested-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>
Reviewed-by: Matt Ingenthron <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@couchbase.com>

dewolfe/couchbase-ruby-client,dewolfe/couchbase-ruby-client