only defines "be_profane" if RSpec is loaded

Loading the gem in a rails project without RSpec loaded is not possible, so I propose this if-block to check if any RSpec::Matchers class is defined.
adds a symbol :international to use the international list
updates the readme with blacklist symbols

:default and :international for config.blacklist=
minor: added Ruby 2.0 to the list of supported rubies

works well and all tests pass
Merge branch 'patch-1'

* patch-1:
  only defines "be_profane" if RSpec is loaded