Highlight numbers in Python import names properly
Summary: This was a typo I made when porting the Pygments lexer.
Test Plan: Made a paste with "import webapp2_extras" and saw that the whole "webapp2_extras" was blue (unlike before, when only "webapp" was).
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: epriestley, Korvin
Differential Revision: https://secure.phabricator.com/D10418