Font Awesome 4.0.3, enum classes

Hi,

I've replaced the enum by a c++11 enum class. So I changed the type of the parameters accordingly.
I used the occasion to switch the font to version 4.0.3 and renamed the file so that we can know the version just by looking at it.

So now icons are called like `fa::signin` . fa stands for font awesome and the new `fa-<icon name>` syntax.

I unfortunately had to rename `linux`, `windows`, `android` and `ios` by suffixing them by `icon` because some of these names are used as pre-processor constants with most compilers.