Use uts instead of date['#text'] conversion

Hi,
there is a little problem when someone changing timezone (like me on a trip). 
Last.fm doesn't send information about timezone it sends time according to user
settings and IIRC UTC is default and `Date()` gives time according to locales. 
My question is why not to use `uts` field ? It's much easier than conversion and gives
correct result for different timezones.
 
Please consider my pull request as a fix.