Fixed error and added style tag to list of ignored tags

I was getting a "superclass mismatch for class RubyPants (TypeError)" error due to the fact that in version.rb, RubyPants wasn't subclassed from String. I fixed that, plus I added style to the list of tags that are ignored for processing. That way something like ```<style>background: url("myimage.jpg");</style>``` won't be corrupted.