Adding minishift-unstable for minishift 1.0.0-beta.1 (#3046)

Casks/minishift-beta.rb

@@ -0,0 +1,16 @@
+cask 'minishift-beta' do
+  version '1.0.0-beta.1'
+  sha256 '2d4020615bd86b814c678fedbf6072488101c26298a90fb081904c6913d88497'
+
+  url "https://github.com/minishift/minishift/releases/download/v#{version}/minishift-#{version}-darwin-amd64.tgz"
+  appcast 'https://github.com/minishift/minishift/releases.atom',
+          checkpoint: 'f78e6fe63a0e0f8f3cae4f97daebe8528e8a38a7d023c6630598b128ee6c8fed'
+  name 'Minishift'
+  homepage 'https://github.com/minishift/minishift'
+
+  binary 'minishift', target: 'minishift'
+
+  postflight do
+    set_permissions "#{staged_path}/minishift", '0755'
+  end
+end