Checks if XDA_DATA_HOME in os.environ before use

Additionally when XDA_DATA_HOME doesn't exist the cookie jar location
defaults to os.environ["HOME"] + '.local/share/uzbl/cookies.txt'
however when these strings are concatenated they are missing the path
seperator '/'. Problem solved by using the builtin os.path.join to join
the environ path and jar location.

diff --cc AUTHORS
index 05271cb,05271cb..031a634
--- 1/AUTHORS
--- 2/AUTHORS
+++ b/AUTHORS
@@@ -29,6 -29,6 +29,7 @@@ Contributors
      (kmeaw) - fix for multibyte utf8 characters segfault
      (evocallaghan) - tiny patches
      Aaron Griffin (phrakture) - Makefile patches to build on OSX
++    Mason Larobina - os.environ.keys() & os.path.join fix in cookies.py
  
  Originaly based on http://trac.webkit.org/browser/trunk/WebKitTools/GtkLauncher/main.c
  Which is  copyrighted: