[docs] Remove duplicate word (#57)

Author: kant

Readme.md

@@ -6,7 +6,7 @@ Default socket.io in-memory adapter class.
 ## How to use
 
 This module is not intended for end-user usage, but can be used as an
-interface to inherit from from other adapters you might want to build.
+interface to inherit from other adapters you might want to build.
 
 As an example of an adapter that builds on top of this, please take a look
 at [socket.io-redis](https://github.com/learnboost/socket.io-redis).