Add support for @enum, @const, @override, @extends and notify unsupported tags

Hey @redmunds, this is a possible approach for #44.

As much as I thought about it, I couldn't think of a nice way of showing a list of tags anywhere that could not be potentially harmful. Imagine if we were to list an `@example` code as requested in #66...

What this does, for now, is to warn the user that an unsupported tag has been found. Additionally, it collects them all in an `unsupported` array in the comment, so if you or @larz0 can think of a nice place to put it, it's there for the taking ;)

Finally, I've added support for all the tags in Brackets code that weren't supported right now, so at least we have that covered. @redmunds, @larz0 what do you think? Could any of these cases be improved somehow?
- `@extends`
![screen shot 2014-06-19 at 7 02 27 pm](https://cloud.githubusercontent.com/assets/905006/3331019/e3aee186-f7d7-11e3-9f2a-784178960f6f.png)

- `@const`
![screen shot 2014-06-19 at 7 19 17 pm](https://cloud.githubusercontent.com/assets/905006/3331020/e3aef18a-f7d7-11e3-85b8-69209f430b4d.png)

- `@overrides`
![screen shot 2014-06-19 at 7 27 58 pm](https://cloud.githubusercontent.com/assets/905006/3331021/e3b1e3f4-f7d7-11e3-8405-f69ad4487e9d.png)

- `@enum`
![screen shot 2014-06-19 at 7 28 27 pm](https://cloud.githubusercontent.com/assets/905006/3331022/e3b2e74a-f7d7-11e3-963a-e8cb6ba6ab5c.png)

 
Why is **type** processed differently here than for `@type` tag:?

```
    value: _.escape(tag.types.join(", "))
```