Respond to krisleech/wisper#47 issue

Remove the should syntax from spec_helper to only use expect syntax
Fix the following specs to use the expect syntax
  these are all the specs that was using should syntax

-wisper_spec
-rspec_extensions_spec
-simple_example_spec
-integration_spec
-global_subscribers_spec
-publisher_spec
Merge pull request #54 from artmees/master

Convert the specs to use the `expect` syntax instead of the `should` syntax