Fixes wrong merge of options passed to GoodData::Domain#find_user_by_login

Fixes #356
Fix test
Fixed PR
Fix issues
Merge branch 'master' of https://github.com/gooddata/gooddata-ruby into fix-find-user-by-login
Merge pull request #359 from korczis/fix-find-user-by-login

Fixes wrong merge of options passed to GoodData::Domain#find_user_by_log...