Merge pull request #127 from joe1chen/memcached-rails-fix-write-unless-exist

Add support for Memcached::Rails write option :unless_exist
Merge pull request #125 from joe1chen/fix-memcached-rails-fetch

Fix the Memcached::Rails fetch method to work when no block is given.
Fix Memcached::Rails read to allow nil options to be passed.
Merge remote-tracking branch 'origin/memcached-rails-fix-read-with-nil-options' into integration