Fix method redefinition warnings.
Remove existing deprecation code in favor of that from rspec-expectations.
Change all deprecation warnings to use new deprecation code.
Merge pull request #291 from warningfree/fix_warnings

Fix method redefinition warnings.
Merge pull request #292 from warningfree/fix_deprecation_warnings

Add rspec-expectation's deprecation code and fix deprecation warnings
fix an internal spec
defer to rspec-core when available for warning about deprecations
move deprecation message inline with core