Massively obliterate the syntax file

Based on discussion with Evan and others [here](https://groups.google.com/forum/#!searchin/elm-discuss/pygments/elm-discuss/RXhWQ650y2Y/qhbF-DDBrXsJ), I think this updated syntax file is more in line with Elm 0.14 as well as my own preferences (no special treatment for standard libs).