failure_message_for_should is deprecated

[mike-zenith]

Hi!

Ive just started using capistrano-spec and i got the following deprecation warning:

`failure_message_for_should` is deprecated. Use `failure_message` instead. 

I would like replace failure_message_for_should to failure_message and add a pull request in the near future if its possible :)

oh, my spec:

$ gem --version
1.8.23
$ ruby --version
ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux]
$ cat Gemfile
source :gemcutter

gem "capistrano"

group :development do
  gem "rspec", ">= 2.5.0"
  gem "bundler", ">= 1.0.9"
  gem "capistrano-spec", :git => "git://github.com/technicalpickles/capistrano-spec.git", :branch => "master"
end

[technicalpickles]

What version of rspec are you using? Depending on when failure_message was introduced, it might get tricky to support multiple versions of rspec.

I'm not actively using this library so won't be fixing this myself anytime soon, but I'm happy to review pull requests (I use The Pull Request Hack to add contributors when they have pull requests accepted).