Fix quick start instructions.

Some changes from this discussion https://forum.javascriptmvc.com/#Topic/32525000001690003

@justinbmeyer I tried to make these changes following http://stealjs.com/docs/guides.Contributing.html#section_WebsiteandDocumentation but documentjs won't install. I get the following error when running <code>npm install</code> in steal#gh-pages.

![screen shot 2014-08-02 at 11 25 02](https://cloud.githubusercontent.com/assets/724877/3788251/5ab8cae0-1a5a-11e4-9640-b646d18c292e.png)

I tried installing it manually <code>npm install git://github.com/bitovi/documentjs</code> and it worked, but got an error running <code>node build.js</code>.

![screen shot 2014-08-02 at 11 28 19](https://cloud.githubusercontent.com/assets/724877/3788256/9bf69cbc-1a5a-11e4-9f4f-48849be43820.png)

Finally, I tried those same steps removing my global grunt-cli and it worked as expected both development / production modes.