Fixed deleting items

Hi, love your work for this repo, very useful.
However, deleting does not work, results in the error below, so I suggest this fix.



error:

REQUEST { method: 'DEL',
  uri: 'https://cloud9ide.zendesk.com/api/v2/topics/123.json',
  headers:
   { Authorization: 'Basic ...',
     'Content-Type': 'application/json',
     Accept: 'application/json' },
  body: '{}',
  jar: { cookies: [] },
  encoding: null,
  timeout: 240000,
  proxy: null,
  callback: [Function] }
{ statusCode: 405,
  result: '<html>\r\n<head><title>405 Not Allowed</title></head>\r\n<body bgcolor="white">\r\n<center><h1>405 Not Allowed</h1></center>\r\n<hr><center>nginx/1.0.15</center>\r\n</body>\r\n</html>\r\n' }
{ [Error: Zendesk Error (405): Method not Allowed]