Fix argument highlighting when using parentheses

![before][1] ![after][2]

It also adds [type check][1] functions as keywords

[1]: http://cl.ly/image/0Q0Y051J2u2U/before.png
[2]: http://cl.ly/image/0B0P1Z0X3L1Q/after.png
[3]: https://github.com/elixir-lang/elixir/blob/master/lib/elixir/lib/kernel.ex#L687