fix dmg plist parsing problem

should take care of #104

this was a subtle one - after i reorganized the requires, plist/parser
was getting double required, which broke plist parsing and hence dmg
installs

lib/cask.rb

@@ -3,9 +3,11 @@ require 'uri'
 class Cask; end
 class Cask::CLI; end
 
-Dir[File.join(File.dirname(__FILE__), '**', '*.rb')].each { |file| 
-  require file.sub(/^lib\/(.*).rb$/, '\1')
-}
+libdir = File.dirname(__FILE__)
+rubyfiles = Dir[File.join(libdir, '**', '*.rb')]
+rubyfiles.each do |file|
+  require file.sub(/^#{libdir}\/(.*).rb$/, '\1')
+end
 
 class Cask
   include Cask::Actions

lib/cask/installer.rb

@@ -22,7 +22,6 @@ class Cask::Installer
 
     def _with_extracted_mountpoints(path)
       if _dmg?(path)
-        require 'plist/parser'
         File.open(path) do |dmg|
           xml_str = `hdiutil mount -plist -nobrowse -readonly -noidme -mountrandom /tmp '#{dmg.path}'`
           hdiutil_info = Plist::parse_xml(xml_str)

test/cask/installer_test.rb

@@ -14,6 +14,19 @@ describe Cask::Installer do
       application = dest_path/'Caffeine.app'
       application.must_be :directory?
     end
+
+    it "works with dmg-based casks" do
+      transmission = Cask.load('local-transmission')
+
+      shutup do
+        Cask::Installer.install(transmission)
+      end
+
+      dest_path = HOMEBREW_CELLAR/'local-transmission'/transmission.version
+      dest_path.must_be :directory?
+      application = dest_path/'Transmission.app'
+      application.must_be :directory?
+    end
   end
 
   describe "uninstall" do

test/support/Casks/local-transmission.rb

@@ -0,0 +1,5 @@
+class LocalTransmission < Cask
+  url TestHelper.local_binary('transmission-2.61.dmg')
+  homepage 'http://example.com/local-transmission'
+  version '2.61'
+end