Add support for Papyrus scripts

## Papyrus

Papyrus is a scripting language used by The Elder Scrolls V: Skyrim (and presumably future Bethsoft releases) to implement complex in-game behavior, communicate with external libraries, and in general do the things scripting languages do. Skyrim has an active modding community and several major players within it use Github to manage their projects. 

### Examples of Papyrus usage on Github

* SkyUI: https://github.com/schlangster/skyui/tree/master/dist/Data/Scripts/Source
* Extensible Follower Framework: https://github.com/expired6978/Extensible-Follower-Framework/tree/master/Data/Scripts/Source
* Skaar: https://github.com/alexdunn/skaar/tree/master/scripts
* APPS: https://github.com/heromaster/APPS/tree/master/Scripts/Source
* MountFX: https://github.com/Verteiron/MountFX/tree/master/dist/data/Scripts/Source
* Familiar Faces: https://github.com/Verteiron/FamiliarFaces/tree/master/dist/Data/scripts/Source

Travis CI build seems to be [succeeding](https://travis-ci.org/Verteiron/linguist/builds/39100415).