Update atom-beta (1.8.0-beta1) (#1913)

Casks/atom-beta.rb

@@ -1,11 +1,11 @@
 cask 'atom-beta' do
-  version '1.8.0-beta0'
-  sha256 'ae49d5e638b6f6520fef91832a9d83ac5f78b1acf936821e5f660995d9b11c31'
+  version '1.8.0-beta1'
+  sha256 'da21371945ac51704cd098b1c95e624501d87351307b77687d5adf7bf3d91050'
 
   # github.com/atom/atom was verified as official when first introduced to the cask
   url "https://github.com/atom/atom/releases/download/v#{version}/atom-mac.zip"
   appcast 'https://github.com/atom/atom/releases.atom',
-          checkpoint: 'af7b24046c3d9bd1d97870e1bcff743889349dd9238a60900350eba888e31d54'
+          checkpoint: '389b4b86b343b7bf3ef904f93dfbbf268f0b1dd2736bd9d8a1370d9a64a6113d'
   name 'Github Atom Beta'
   homepage 'https://atom.io/beta'
   license :mit