[Rakefile] Allow to release with changes in the Gemfile.lock file

Rakefile

@@ -62,6 +62,7 @@ namespace :gem do
 
       diff_lines = `git diff --name-only`.strip.split("\n")
       diff_lines.delete('CHANGELOG.md')
+      diff_lines.delete('Gemfile.lock')
 
       if diff_lines.size == 0
         $stderr.puts "[!] Change the version number yourself in lib/cocoapods/gem_version.rb"
@@ -117,7 +118,7 @@ namespace :gem do
     silent_sh "gem install --install-dir='#{tmp_gems}' #{gem_filename}"
 
     # Then release
-    sh "git commit lib/cocoapods/gem_version.rb CHANGELOG.md -m 'Release #{gem_version}'"
+    sh "git commit lib/cocoapods/gem_version.rb CHANGELOG.md Gemfile.lock -m 'Release #{gem_version}'"
     sh "git tag -a #{gem_version} -m 'Release #{gem_version}'"
     sh "git push origin master"
     sh "git push origin --tags"