This line of code makes it impossible to use Mongo::URIParser to connect to a replica set with mixed case names.

For example mongodb://admin:password@hostname:27017/admin?replicaSet=MyReplSet.

      opts = CGI.parse(string_opts).inject({}) do |memo, (key, value)|
        value = value.first
        memo[key.downcase.to_sym] = value.strip.downcase
        memo
      end