Add support for additional group information

See koraktor/steam-condenser#225
Update test fixture for new group data
Also load the URL from group data
Test all group attributes
Fix encoding of test_steam_group.rb for Ruby 1.9
SteamId requires the 'time' stdlib

We use `Time.parse`.
Improve handling of UTF-8 characters in server replies

This works for Ruby 1.9+. On Ruby 1.8 be sure to set $KCODE to 'UTF-8'.
Version bump to 1.3.8
Merge branch '1.3-stable'