Create a clean master branch, add a grunt.js based build script and removed 'build' folder with gh-pages clone

Second attempt on correct branch

FIxed #1042

I've removed the `build` folder with the gh-pages clone from the 3.2.0-wip branch and added a submodule to the original gh-pages branch for those who need the branch in their local copy. I've added a grunt.js based build script that compiles the LESS styles into CSS, minifies them and creates a font-awesome.zip file from all project files in 3.2.0-wip. Read the updated README.md for install and usage instructions for grunt. There is also a second target defined in the grunt buildfile. After checkout of the `gh-pages` submodule run

```
grunt pages
```

to compile the sourcefiles into the `gh-pages` submodule folder, which you then can commit to the original branch. 

This way Font Awesome can easily be integrated in automated build scripts and can be made ready for bower install without providing tons of unnecessary files.