Highlighting of capitalized atoms (modules) when used as structs

[whatyouhide]

Hey there, I'm superhappy #166 came to a resolution and now is included into emacs-elixir :).

There's still a little issue with the highlighting of modules though: it doesn't work when modules are preceded by a % character (= structs).

Since Conn in the screenshot is highlighted correctly even if preceded by a ., I hope that adding support for % as well is a quick fix :). Thanks!