Update ImageOptim dependency to 0.18.0

`ImageOptim` now supports a `skip_missing_workers` option, which allows
us to not have to manually disable `pngout`.

Change the hook to use this option and update the dependency.

Change-Id: Iea175e9139b7f8e64d75a1da806d70241e618d37
Reviewed-on: http://gerrit.causes.com/45274
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>

Author: sds

CHANGELOG.md

@@ -7,6 +7,8 @@
 * Fix installer to work with Overcommit hooks created via `GIT_TEMPLATE_DIR`
 * Fix hook runner to not display skip message unless hook would have actually
   run
+* Change `ImageOptim` hook to use `skip_missing_workers` option and update
+  dependency to 0.18.0
 
 ## 0.19.0
 * Add `--no-pngout` flag for `image_optim` command on `:fail` message

lib/overcommit/hook/pre_commit/image_optim.rb

@@ -19,7 +19,7 @@ def run
         return :fail,
           "The following images are optimizable:\n#{optimized_images.join("\n")}" \
           "\n\nOptimize them by running:\n" \
-          "  image_optim --no-pngout #{optimized_images.join(' ')}"
+          "  image_optim --skip-missing-workers #{optimized_images.join(' ')}"
       end
 
       :pass
@@ -28,10 +28,10 @@ def run
     private
 
     def optimize_images(image_paths)
-      image_optim = ::ImageOptim.new(:pngout => false)
+      image_optim = ::ImageOptim.new(:skip_missing_workers => true)
 
       optimized_images =
-        image_optim.optimize_images!(image_paths) do |path, optimized|
+        image_optim.optimize_images(image_paths) do |path, optimized|
           path if optimized
         end
 

overcommit.gemspec

@@ -28,6 +28,6 @@ Gem::Specification.new do |s|
 
   s.add_dependency             'childprocess', '>= 0.5.1'
 
-  s.add_development_dependency 'image_optim', '~> 0.15.0'
+  s.add_development_dependency 'image_optim', '~> 0.18.0'
   s.add_development_dependency 'rspec', '~> 3.0'
 end