Improve error handling while parsing XML data

Fixes koraktor/steam-condenser#224
Add support for additional group information

See koraktor/steam-condenser#225
Fix phpDoc broken by find/replace
Unified cache() methods of community classes
Fix broken cache tests
Fix composer.json for version 1.3.6

Closes koraktor/steam-condenser#228
Merge branch 'fix-composer-1.3.6' into 1.3-stable
Version bump to 1.3.7
Merge branch '1.3-stable'