Remove cucumber monkey patch translating steps:

It was initially added to allow reuse of aruba cucumber steps, using
`must' instead of `should'. This is creating more harm than good, hence
we remove it and implements all missing steps, using aruba API.

features/steps/execution_steps.rb

@@ -0,0 +1,3 @@
+Then /^the exit status must be (\d+)$/ do |exit_status|
+  assert_exit_status exit_status.to_i
+end