Fixed a regression in SteamId and SteamGroup's error handling

SteamCondenserError wouldn't be reraised, but cause a new error so the
initial cause would be lost.
Updated multi_json dependency to 1.6.0
Version bump to 1.3.4
Version bump to 1.3.4.1

The gem with version 1.3.4 has been yanked because it was built from
the wrong branch.
Merge branch '1.3-stable'