Out of the Cellar, into the Caskroom

Install casks into HOMEBREW_PREFIX/"Caskroom" instead of the Cellar.
This prevents us from colliding with normal Homebrew Formulae.

NOTE: this will be a breaking change, with the following effects:

- all installed casks will no longer be reported as installed
- orphans all existing casks in the Cellar
- no automated facility for cleanup or migration of existing casks

refs #38, where we can discuss the implications of this before cutting a
new release

lib/cask.rb

@@ -18,8 +18,8 @@ class Cask
     HOMEBREW_PREFIX.join "Library", "Taps"
   end
 
-  def self.cellarpath
-    HOMEBREW_CELLAR
+  def self.caskroom
+    HOMEBREW_PREFIX.join "Caskroom"
   end
 
   def self.appdir
@@ -32,6 +32,7 @@ class Cask
   
   def self.init
     HOMEBREW_CACHE.mkpath unless HOMEBREW_CACHE.exist?
+    caskroom.mkpath unless caskroom.exist?
     appdir.mkpath unless appdir.exist?
   end
 
@@ -57,7 +58,7 @@ class Cask
   end
 
   def destination_path
-    HOMEBREW_CELLAR.join(self.title).join(self.version)
+    self.class.caskroom.join(self.title).join(self.version)
   end
 
   def installed?

lib/cask/cli.rb

@@ -78,6 +78,10 @@ class Cask::CLI
       puts Cask::CLI.commands.map {|c| " - #{c.downcase}: #{_help_for(c)}"}.join("\n")
     end
 
+    def help
+      ''
+    end
+
     def _help_for(command)
       Cask::CLI.lookup_command(command).help
     end

test/cask/installer_test.rb

@@ -9,7 +9,7 @@ describe Cask::Installer do
         Cask::Installer.install(caffeine)
       end
 
-      dest_path = HOMEBREW_CELLAR/'local-caffeine'/caffeine.version
+      dest_path = Cask.caskroom/'local-caffeine'/caffeine.version
       dest_path.must_be :directory?
       application = dest_path/'Caffeine.app'
       application.must_be :directory?
@@ -22,7 +22,7 @@ describe Cask::Installer do
         Cask::Installer.install(transmission)
       end
 
-      dest_path = HOMEBREW_CELLAR/'local-transmission'/transmission.version
+      dest_path = Cask.caskroom/'local-transmission'/transmission.version
       dest_path.must_be :directory?
       application = dest_path/'Transmission.app'
       application.must_be :directory?