Added MainJSONHandler which handles the json response for
the main page.
Refactored the code to actually write the json values to the
page into the JSONHandler class.  Both our other JSON classes
inherit from JSONHandler now.
Fixed a bug in PermalinkJSONHandler where we were still
using self.write_dict_as_json instead of self.write_json.
Updated the main program to handle the main page json
response.