Return :warn instead of :fail on BundleCheck

When rebasing, returning :fail will abort rebase and the repository ends
up with a detached HEAD. Rebase becomes impossible unless you install
the needed gems first.

Change-Id: I6bc22934554dc4b422398082ccf076de97fd0251
Reviewed-on: http://gerrit.causes.com/35952
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>

Author: htanata

CHANGELOG.md

@@ -6,6 +6,8 @@
   and commit message body widths
 * Fix bug where committing a change with only file deletions would result
   in those changes not being committed
+* Warn instead of failing when gem dependencies are out of date in
+  `BundleCheck` post-checkout hook
 
 ## 0.6.2
 

lib/overcommit/hook/post_checkout/bundle_check.rb

@@ -7,7 +7,7 @@ def run
         return :warn, 'bundler not installed -- run `gem install bundler`'
       end
 
-      return :bad if dependencies_changed? && !dependencies_satisfied?
+      return :warn if dependencies_changed? && !dependencies_satisfied?
 
       :good
     end

spec/overcommit/hook/post_checkout/bundle_check_spec.rb

@@ -43,7 +43,7 @@
     context 'and the dependencies are not satisfied' do
       let(:satisfied) { false }
 
-      it { should fail_check }
+      it { should warn }
     end
   end
 end