Added missing code to take the zone value from knife config file along with test-cases.
Taking the google compute zone value from knife config file.
Updated server create and delete similar to list, refactored list to be little more informative.
Adding test-case for server create taking values from knife.rb
Added test-case for server delete taking values from knife.rb
Merge pull request #15 from opscode/adamed-OC-7868-google-server-list

OC-7868: Knife google plug-in does not read cli switches from knife.rb