spec refactoring: rename subject with intention revealing name
spec refactoring: rename subject with intention revealing name

- even though 'object' is no less generic than 'subject', it makes it
  more clear that we're talking about a generic object.

maclover7/rspec-mocks,ducthanh/rspec-mocks,rspec/rspec-mocks,zephyr-dev/rspec-mocks,rwz/rspec-mocks,zephyr-dev/rspec-mocks,AEgan/rspec-mocks,edwardpark/rspec-mocks,ducthanh/rspec-mocks,samphippen/rspec-mocks,edwardpark/rspec-mocks,h4ck3rm1k3/rspec-mocks,rspec/rspec-mocks,telekomatrix/rspec-mocks,thoughtbot/rspec-mocks,thoughtbot/rspec-mocks,h4ck3rm1k3/rspec-mocks,samphippen/rspec-mocks,maclover7/rspec-mocks,AEgan/rspec-mocks,rwz/rspec-mocks,telekomatrix/rspec-mocks