set $RUBIES after `bchruby` method is defined
use `id -u` instead of `$UID` in fish shell
return correct exit code on chruby error
set $GEM_ROOT
use correct variable to check if GEM_PATH should be defined
make GEM_HOME and GEM_PATH optional for root users
add initial batch of tests
ignore installed test rubies in test/opt
add initial travis.yml config