Merge pull request #166 from jniehus/master

Add convenience method to Json struct to output pretty strings
Renamed toJson/toPrettyJson to writeJsonString/writePrettyJsonString and improved the ddoc comments.
Removed uses of toPrettyJson (replaced by writePrettyJsonString).
Removed the "deprecated" tag of the compatibility alias HttpRequest.url for now and removed all uses of it. Fixes issue #167.
Merge remote-tracking branch 'upstream/master'