Add Audacity Nightly (#3702)

* Add Audacity Nightly

* Update Audacity Nightly to use dynamic url

Casks/audacity-nightly.rb

@@ -0,0 +1,28 @@
+cask 'audacity-nightly' do
+  version :latest
+  sha256 :no_check
+
+  # audacity.homerow.net was verified as official when first introduced to the cask
+  url do
+    require 'open-uri'
+    base_url = 'http://www.audacity.homerow.net/index.php?dir=mac/'
+    builds_url = "#{base_url}&sort=m_time&sort_mode=d"
+    open(builds_url) do |builds|
+      pattern = %r{(?<=\/index.php\?dir=mac\/)audacity-nightly-\d{4}\.\d{2}\.\d{2}-\d{2}\.\d{2}-[[:xdigit:]]{7}(?=\/\">)}
+      latest_build_directory = "#{base_url}#{pattern.match(builds.read)}"
+      open(latest_build_directory) do |build|
+        pattern = %r{(?<=\/index.php\?dir=mac\/audacity-nightly-\d{4}\.\d{2}\.\d{2}-\d{2}\.\d{2}-[[:xdigit:]]{7}\/&amp;file=)audacity-macosx-\d.*\.dmg(?=\">)}
+        latest_build_filename = pattern.match(build.read).to_s
+        "#{latest_build_directory}&file=#{latest_build_filename}"
+      end
+    end
+  end
+  name 'Audacity'
+  homepage 'http://www.audacityteam.org/'
+
+  depends_on macos: '>= :snow_leopard'
+
+  app 'Audacity.app'
+
+  zap delete: '~/Library/Application Support/audacity'
+end