Optionally override the default comment regex

Hi, what do you think about this? I'd like to be able to support different types of comments (eg. `//` instead of `///`).  Everything should still be backwards compatible until you opt-in to the custom format.
In Javascript the RegEx has a state. Would be good to reset it before using it:
```js
this.docCommentRegEx.lastIndex = 0;
```