Update README.md: fix link to build instructions

Author: christopherthielen

README.md

@@ -32,7 +32,7 @@ Check out the sample app: http://angular-ui.github.io/ui-router/sample/
 ## Get Started
 
 **(1)** Get UI-Router in one of 4 ways:
- - clone & [build](#developing) this repository
+ - clone & [build](CONTRIBUTING.md#developing) this repository
  - [download the release](http://angular-ui.github.io/ui-router/release/angular-ui-router.js) (or [minified](http://angular-ui.github.io/ui-router/release/angular-ui-router.min.js))
  - via **[Bower](http://bower.io/)**: by running `$ bower install angular-ui-router` from your console
  - or via **[npm](https://www.npmjs.org/)**: by running `$ npm install angular-ui-router` from your console