[Gemspec] Bump Xcodeproj to 1.3.1

Gemfile.lock

@@ -24,10 +24,10 @@ GIT
 
 GIT
   remote: https://github.com/CocoaPods/Xcodeproj.git
-  revision: 1bee869af047a36cab67ee108f3477144749ba95
+  revision: c8b7277072c3c2432ac99ef9b45cd1a6d181409e
   branch: master
   specs:
-    xcodeproj (1.3.0)
+    xcodeproj (1.3.1)
       activesupport (>= 3)
       claide (>= 1.0.0, < 2.0)
       colored (~> 1.2)
@@ -111,7 +111,7 @@ PATH
       gh_inspector (~> 1.0)
       molinillo (~> 0.5.0)
       nap (~> 1.0)
-      xcodeproj (>= 1.3.0, < 2.0)
+      xcodeproj (>= 1.3.1, < 2.0)
 
 GEM
   remote: https://rubygems.org/

cocoapods.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'cocoapods-trunk',       '>= 1.0.0', '< 2.0'
   s.add_runtime_dependency 'cocoapods-try',         '>= 1.1.0', '< 2.0'
   s.add_runtime_dependency 'molinillo',             '~> 0.5.0'
-  s.add_runtime_dependency 'xcodeproj',             '>= 1.3.0', '< 2.0'
+  s.add_runtime_dependency 'xcodeproj',             '>= 1.3.1', '< 2.0'
 
   ## Version 5 needs Ruby 2.2, so we specify an upper bound to stay compatible with system ruby
   s.add_runtime_dependency 'activesupport', '>= 4.0.2', '< 5'