Fixed NameError: global name 'updated' is not defined

Fixes traceback
lib/python2.7/site-packages/feedgen/feed.py", line 447, in lastBuildDate
return updated( lastBuildDate )
NameError: global name 'updated' is not defined
Merge pull request #8 from ngulden/master

Fixed NameError: global name 'updated' is not defined