Switching call to protected 'offset' method

in TZInfo 1.0 offset was made protected.  Using utc_total_offset() method instead of offset.utc_total_offset

I have no idea why on a particular set of machines, when I run bundle install, it uses tzinfo 1.0.1 instead of 0.3.35 specified in Gemfile.lock.  I'm too new to Ruby unfortunately....

See: Issue #370