Support rpm on be_installed` matcher

[hayato1980]

This pull request following test.

describe package('httpd') do
  it { should be_installed.by('rpm').with_version('2.2.15-28.el6') }
end

until apply this patch, following result.

 1) Package "httpd" 
     Failure/Error: it { should be_installed.by('rpm').with_version('2.2.15-28.el6') }
     ArgumentError: `be_installed` matcher doesn't support rpm

       `be_installed` matcher doesn't support rpm

[mizzy]

Thanks.

You should use alias method rather than defining a new method like this.

def check_installed(package,version=nil)
  cmd = "rpm -q #{escape(package)}"
  if ! version.nil?
    cmd = "#{cmd} | grep -w -- #{escape(version)}"
  end
  cmd
end

alias :check_installed_by_rpm :check_installed

[hayato1980]

Just as you say.

I revert and reimplement by alias.

[mizzy]

Thanks!