add `brew cask info` command

thanks to @passcod for original implementation on his fork

refs #72

lib/cask/cli/info.rb

@@ -0,0 +1,39 @@
+class Cask::CLI::Info
+  def self.run(*cask_names)
+    cask_names.each do |cask_name|
+      begin
+        cask = Cask.load(cask_name)
+        puts info(cask)
+      rescue CaskUnavailableError => e
+        onoe e
+      end
+    end
+  end
+
+  def self.help
+    "displays information about the cask of the given name"
+  end
+
+  def self.info(cask)
+    installation = if cask.installed?
+                     "#{cask.destination_path} (#{cask.destination_path.abv})"
+                   else
+                     "Not installed"
+                   end
+
+    <<-PURPOSE.undent
+    #{cask}: #{cask.version}
+    #{cask.homepage}
+    #{installation}
+    #{github_info(cask)}
+    PURPOSE
+  end
+
+  def self.github_info(cask)
+    tap = cask.title
+    tap = cask.class.all_titles.grep(/#{tap}$/).first unless tap =~ /\//
+    tap, name = tap.split "/"
+    user, repo = tap.split "-"
+    "https://github.com/#{user}/#{repo}/commits/master/Casks/#{name}.rb"
+  end
+end

test/cli/info_test.rb

@@ -0,0 +1,29 @@
+require 'test_helper'
+
+describe Cask::CLI::Info do
+  it 'displays some nice info about the specified cask' do
+    lambda {
+      Cask::CLI::Info.run('alfred')
+    }.must_output <<-CLIOUTPUT.undent
+      alfred: 1.3.2_265
+      http://www.alfredapp.com/
+      Not installed
+      https://github.com/phinze/cask/commits/master/Casks/alfred.rb
+    CLIOUTPUT
+  end
+
+  it 'works for multiple casks' do
+    lambda {
+      Cask::CLI::Info.run('alfred', 'firefox')
+    }.must_output <<-CLIOUTPUT.undent
+      alfred: 1.3.2_265
+      http://www.alfredapp.com/
+      Not installed
+      https://github.com/phinze/cask/commits/master/Casks/alfred.rb
+      firefox: 17.0.1
+      http://www.mozilla.org/en-US/firefox/
+      Not installed
+      https://github.com/phinze/cask/commits/master/Casks/firefox.rb
+    CLIOUTPUT
+  end
+end