fix for #31, thanks ashish.tonse

git-svn-id: https://oauth.googlecode.com/svn/code/python@847 f7ae4463-c52f-0410-a7dc-93bad6e629e8

Author: leah.culver

oauth/oauth.py

@@ -124,7 +124,8 @@ def to_header(self, realm=''):
         # add the oauth parameters
         if self.parameters:
             for k, v in self.parameters.iteritems():
-                auth_header += ', %s="%s"' % (k, escape(str(v)))
+                if k[:6] == 'oauth_':
+                    auth_header += ', %s="%s"' % (k, escape(str(v)))
         return {'Authorization': auth_header}
 
     # serialize as post data for a POST request