Rename PTH to Redacted and fix invalid User-Agent (Again)

This is a duplicate of albshin's PR as I got impatient waiting for him
to submit it to the develop branch with the addition of removing the
previous user agents and replacing them with Headphones as the agent.
Redacted considers falsifying the agent as a bannable offence.

From albshin's PR;
"Changes all instances of PassTheHeadphones to Redacted. Removed the URL
option for Redacted as it's unnecessary(?).

Fixed a bug in the pyGazelle library in which the User-Agent was invalid
due to a missing space. Should work now for Redacted."

lib/pygazelle/api.py

@@ -11,6 +11,7 @@ import sys
 import json
 import time
 import requests as requests
+import headphones
 
 from .user import User
 from .artist import Artist
@@ -32,9 +33,7 @@ class GazelleAPI(object):
     default_headers = {
         'Connection': 'keep-alive',
         'Cache-Control': 'max-age=0',
-        'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3)'\
-                      'AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.79'\
-                      'Safari/535.11',
+        'User-Agent': 'Headphones/%s' % headphones.CURRENT_VERSION,
         'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9'\
                   ',*/*;q=0.8',
         'Accept-Encoding': 'gzip,deflate,sdch',