Fix svntweet.py for the changes to svnpubsub.  Followup to r1432778.

Also uses posixpath instead of os.path to deal with fspaths so it can work on  
OS'es that use something other than '/' as the path separator.

[in tools/server-side/svnpubsub]

* svntweet.py
  (documentation): Remove /xml from suggested config.
  (imports): Remove xml.sax as we no longer support xml and pull in posixpath.
  (Revision): Remove and replace with...
  (Commit): New class.
  (StreamHandler): Remove and replace with...
  (JSONRecordHandler): New class.
  (XMLHTTPStream): Remove and replace with...
  (JSONHTTPStream): New class.
  (connectTo): Use JSONHTTPStream instead of XMLHTTPStream.
  (BigDoEverythingClasss._normalize_path, BigDoEverythinglass.build_tweet):
    Use posixpath not os.path.
  (BigDoEverythingClasss.build_tweet, BigDoEverythingClasss.commit): Take a
    Commit object instead of Revision object.
  (BigDoEverythignClasss.build_tweet):  Use new shorter link.



git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1435447 13f79535-47bb-0310-9956-ffa450edef68