Syntax: incorrectly highlights paren after `defmodule`

<img width="309" alt="image 2018-08-02 at 12 25 25 pm" src="https://user-images.githubusercontent.com/6093002/43597446-1490911c-9650-11e8-8f8a-239e29e0b392.png">

syn stack at open paren: `hi<elixirModuleDeclaration> trans<elixirModuleDeclaration> lo<Type>`