Implement Haskell Formatter

[carymrobbins]

Pull request #87 implemented code style settings; however, we need a formatter so the code sample will update the indents accordingly. This may also resolve #80 for auto-indent support.

Here's the official IntelliJ documentation on the topic -

https://confluence.jetbrains.com/display/IDEADEV/Developing+Custom+Language+Plugins+for+IntelliJ+IDEA#DevelopingCustomLanguagePluginsforIntelliJIDEA-CodeFormatter

I will once again defer to the intellij-erlang plugin as a good example of how to accomplish this -

https://github.com/ignatov/intellij-erlang/tree/master/src/org/intellij/erlang/formatter