Allow for parallel test execution.

script/cibuild

@@ -3,5 +3,4 @@
 set -e
 
 script/branding
-script/proof
-script/test
+ls -1 script/{test,cucumber,proof} | xargs -P 3 -L 1 /bin/bash

script/cucumber

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+bundle exec rake features

script/test

@@ -14,4 +14,4 @@ fi
 
 set -x
 
-bundle exec rake
+bundle exec rake test