#1048: Create a JSONP writer

For phpDocumentor to create templates that consume content using XHR requests we
actually need to do JSONP requests to retrieve content. This is because docs
made with phpDocumentor are often read offline without the use of a web server.

The absence of a web browser has the disadvantage that XHR requests are not
possible with the single exception of JSONP requests because those are not
hindered by cross domain request restrictions.
#1048: Process review feedback

During code review a few points of feedback have emerged and while testing
with Yii I also found a bug that crashed parsing. All these points have
been fixed in this commit
#1048: Fix broken unit test
Merge pull request #1446 from mvriel/feature/1048

[Merge after 2.8] #1048: Create a JSONP writer