rearrange spec for Netscaler::ServiceGroup and fixing bugs in the tests
Added stub_it method for WebHTTPMock to simplify each Mock subclasses
Made use of stub_it in rspec Mock for Netscaler::Server
Added rspec for Netscaler::ServiceGroup for enable_server / disable_server / list_servers / bind / unbind
added conditions if argument is an array or Hash in send_action method of Netscaler::BaseObject
Added bind / unbind and list_servers methods to Netscaler::ServiceGroup