don't fail if response body is empty
test empty response body
test remove_credentials SUSE::Connect::System method
add SUSE::Connect::System.remove_credentials
test SUSE::Connect::Client.deregister! method
add deregister/unregister a system to SUSE::Connect::Client
add webmock for deregister call
test SUSE::Connect::Api.deregister response and status code
add method for deregister call
fix rubocop warnings
stub System.remove_credentials instead of File operations
mock registered? method
Merge pull request #46 from SUSE/review_140409_deregister_system_with_connect

[Review] Request from 'vlewin' @ 'SUSE/connect/review_140409_deregister_system_with_connect'