allow has_received to take a block to match against passed arguments to mocked method
remove unnecessary specs on receive matcher
ensure curly-brace block passed to have_received takes precedence over do-end
foo ||= bar is nicer syntax than foo = foo || bar
Merge pull request #367 from timcowlishaw/feature-have-received-takes-a-block-and-yields-arguments

allow has_received to take a block to match against passed arguments.