Improve test suite performance with aruba wrapper:

* Implement ArubaProgramWrapper in cucumber env;
* Tag a few features to not use the wrapper as aruba doesn't support yet
  interactive testing with in process mode, and reported program name
  will not be the correct one;
* Assign required standard streams to CLI and Env classes.

features/recipe_ask.feature

@@ -1,5 +1,6 @@
 Feature: `ask' recipe keyword
 
+  @exec
   Scenario: prompts user with a list of choices on standard output
     Given a recipe with:
       """