Set all missing Weather.com XML tag values to an empty string (Fixes issue 34)
Update version number to 0.3.8

git-svn-id: http://python-weather-api.googlecode.com/svn@161 f8314ed2-3ed7-11de-b232-599c1b3c59e8
Update CHANGELOG and README files for 0.3.8 release

git-svn-id: http://python-weather-api.googlecode.com/svn@162 f8314ed2-3ed7-11de-b232-599c1b3c59e8