Drop $.toJSON and $.parseJSON requirement

Uses JSON.parse and JSON.stringify if present, but will check for
$.toJSON and $.parseJSON if JSON is not supported. Should therefore
be backwards compatible.
Version bump to 0.5.0
Update jquery.jsonrpcclient.js

REMOVED TRAILING WHITESPACE
Merge pull request #23 from Textalk/dev-drop-jquery-json

Dev drop jquery json