support CoffeeTags on moon files

Hi @leafo:

I have been using [CoffeeTags](https://github.com/lukaszkorecki/coffeetags) a lot in my diary work. It clearly lists an outline of the coffeescript file, which saves me a lot time. 

Now I switched to moonscript projects, and found the CoffeeTags can work perfectly on moon files. So I combined the coffeetags vim plugin into the moonscript plugin. And now I can have a nice moonscript code outline in the tagbar.

![moontags](https://cloud.githubusercontent.com/assets/9838/3711034/be79955a-14ba-11e4-9d42-20bf131a7392.png)

is this going to show a warning every time someone runs vim without ruby regardless of whether they have coffeetags installed or not?