Added spec:portability task to test Guard::Compass on Ruby 1.8.6, 1.8…

….7 and 1.9.2

Rakefile

@@ -5,3 +5,17 @@ require 'rspec/core/rake_task'
 RSpec::Core::RakeTask.new(:spec)
 task :default => :spec
 
+namespace(:spec) do
+  desc "Run all specs on multiple ruby versions (requires rvm)"
+  task(:portability) do
+    %w[1.8.6 1.8.7 1.9.2].each do |version|
+      system <<-BASH
+        bash -c 'source ~/.rvm/scripts/rvm;
+                 rvm #{version};
+                 echo "--------- version #{version} ----------\n";
+                 bundle install;
+                 rake spec'
+      BASH
+    end
+  end
+end