cocoapods-beta: init at 1.7.0.beta.3

cocoapods-beta is an alternative attribute for the cocoapods package
that provides the latest beta instead of the stable version.

Also switch to `bundlerApp` so we stop polluting the profile with our
gem dependencies and can get rid of the broken `sandbox-pod` executable.

pkgs/development/mobile/cocoapods/Gemfile.lock

@@ -2,7 +2,7 @@ GEM
   remote: https://rubygems.org/
   specs:
     CFPropertyList (3.0.0)
-    activesupport (4.2.11)
+    activesupport (4.2.11.1)
       i18n (~> 0.7)
       minitest (~> 5.1)
       thread_safe (~> 0.3, >= 0.3.4)
@@ -32,7 +32,7 @@ GEM
       activesupport (>= 4.0.2, < 6)
       fuzzy_match (~> 2.0.4)
       nap (~> 1.0)
-    cocoapods-deintegrate (1.0.3)
+    cocoapods-deintegrate (1.0.4)
     cocoapods-downloader (1.2.2)
     cocoapods-plugins (1.0.0)
       nap
@@ -43,7 +43,7 @@ GEM
       netrc (~> 0.11)
     cocoapods-try (1.1.0)
     colored2 (3.1.2)
-    concurrent-ruby (1.1.4)
+    concurrent-ruby (1.1.5)
     escape (0.0.4)
     fourflusher (2.2.0)
     fuzzy_match (2.0.4)
@@ -59,7 +59,7 @@ GEM
     thread_safe (0.3.6)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
-    xcodeproj (1.8.1)
+    xcodeproj (1.8.2)
       CFPropertyList (>= 2.3.3, < 4.0)
       atomos (~> 0.1.3)
       claide (>= 1.0.2, < 2.0)
@@ -70,7 +70,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  cocoapods
+  cocoapods!
 
 BUNDLED WITH
    1.17.2