Relax nokogiri dependency
Remove trailing whitespaces
Fix variable scope
Add proper logging

Note: log level can be set using VCLOUD_REST_DEBUG_LEVEL and log's
output can be set using VCLOUD_REST_LOG_FILE
Fix require for Minitest > 5
Refactor connection into modules
Move humanization of Bad Request errors to a separate function
Add method to retrieve VM info (cpu & memory)
VM: add methods to set CPUs/Memory info