Fix to ignore httplib2 in string extraction

This resolves the https://github.com/gae-init/gae-init-babel/issues/5 "Bad gettext in httplib2 leading to untranslatable strings" issue, by adding `[ignore: **/httplib2/**.py]` to the `main/translations/babel.cfg` configuration file. Note that order of the patterns seems to be important in the `babel.cfg` file.