Fixup README

Part of the fix is replacing EM integration link for ruby with link to
patch[1] which still on review, but is going to be merged soon. This
patch brings EventMachine support to the couchbase gem and allow to
use the same API set.

[1]: http://review.couchbase.org/23347
Merge pull request #1 from avsej/fixup-readme

Fixup README