Force docs (curies) to be downloaded as JSON.

[bsodzik]

When using iframe there is no control over HTTP headers. If REST service returns data in several formats then application/xml is preferred over application/json by all major browsers. Simple solution to that problem is to use ajax instead of iframe. That is what I implemented in this pull request and would be great if you would like to merge it into your main repository :)

[mikekelly]

it doesn't seem to make sense to use JSON for human readable docs