Update README.md

Fix link to node

Author: mhegazy

README.md

@@ -23,7 +23,7 @@ There are many ways to [contribute](https://github.com/Microsoft/TypeScript/blob
 
 ## Building
 
-In order to build the TypeScript compiler, ensure that you have [Git](http://git-scm.com/downloads) and [Node.js]((http://nodejs.org/) installed.
+In order to build the TypeScript compiler, ensure that you have [Git](http://git-scm.com/downloads) and [Node.js](http://nodejs.org/) installed.
 
 Clone a copy of the repo: