Renaming Project and file to dn-animate-css/dn-animate.css

`animate.css` being very vague, it would be preferable to have it distinguishable from other similar names

I took the liberty to rename the package (npm and bower) to `dn-animate-css` (notice the `-` instead of the `.`)

See this issue for an explanation: https://github.com/ck86/main-bower-files/issues/3

Gruntfile has been updated accordingly. I don't think I have forgotten anything. Feel free to amend as needed