require popen

README.md

@@ -9,6 +9,10 @@ Uses:
 
 ## Installation
 
+Make sure the dependencies are installed on the system:
+
+    apt-get install pngcruch jpegoptim
+
 Add this line to your application's Gemfile:
 
     gem 'under-pressure'

under-pressure.gemspec

@@ -20,5 +20,5 @@ Gem::Specification.new do |gem|
   gem.require_paths = ["lib"]
   gem.files         = Dir.glob("{lib}/**/*") + %w(README.md)
 
-  gem.add_dependency "open4"
+  gem.add_dependency "POpen4" # Handle shelling out nicely
 end