Add comment and ellipsis support to json lexer.

[textshell]

This pull request adds ellipsis support in addition to comment support from pull request 243.

Omitting key/value pairs with the comment syntax (i.e. // ... ) is awkward because if used at the end of an object you need to change the preceeding line to remove a trailing comma. This PR adds an syntax that looks better and also removes the special case when used at the end of an object.

Example:

    {
        "accountId": "someone@example.com",
        "id": "15",
        "addDate": "2015-01-01T00:00:00",
        "lastChangeDate": "2015-01-01T00:00:00",
        ...
    }

[jneen]

This is really cool! However, I'm a little hesitant to add it to the main json lexer. Would it be possible to create a new lexer for this instead? Maybe json-doc? You could even subclass JSON and use the prepend / append interface (see C++ for an example).

[jneen]

(oops, accidentally closed)

[textshell]

I'm implementing it as subclass of JSON which seems to be working out well.
Do you think it will be ok to keep json-doc in the javascript.rb file?
Do you have any advise what that subclass should use for filenames and mimetypes? I guess if i don't set anything they will be inherited from the JSON class, which might confuse auto detection?
C++ solves that by actually having a mime type and file extensions that can be used there, which is not really the case here.

[textshell]

Did you have a chance to look at this? Will this work, or it there still something to fix?

[textshell]

@jneen ping?

[jneen]

Sorry for the delay. Looks fantastic, thank you.