Use the python url parser for encoding arguments

Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>

slack/api.py

@@ -2,12 +2,13 @@
 # Copyright 2015 (c) Anna Schumaker
 #
 import json
+from urllib import parse
 from urllib import request
 
 __SLACK_SERVER = "https://slack.com/api"
 
 def call(method, **kwargs):
-    args = "&&".join("%s=%s" % x for x in kwargs.items())
+    args = parse.urlencode(kwargs)
     with request.urlopen("%s/%s?%s" % (__SLACK_SERVER, method, args)) as req:
         return json.loads(req.read().decode())
     return {"ok" : False}