Change to use YAML load instead of Psych

Change-Id: Ia120155e7c90d17ecfbbbd892c958cda9813ec55
Add Client.initialize to Client OM
Move unused methods into the private block
Move rest_logger from client.rb to connection.rb
Refactor response_mapping into a separate class
Add unit test for client.rb to check reading settings from argument or default
Add unit test for connection.rb
Remove all namespaces & modules from spec files.
spec: fix formatting
fix formatting

Change-Id: I624986c5ae1d87bb8c6acd56a6d498c041be5b5c