Implement dry run mode

features/cli/dry_run.feature

@@ -0,0 +1,11 @@
+Feature: CLI dry run option
+
+  Scenario: perfoms a trial run without applying actions
+    Given a recipe with:
+      """
+      task :say_hello do
+        echo 'hello'
+      end
+      """
+    When I successfully execute the recipe with option -n
+    Then the output must not contain "hello"

features/cli/usage.feature

@@ -5,5 +5,5 @@ Feature: CLI usage
     Then the exit status must be 64
     And the output must contain exactly:
       """
-      Usage: producer [-v] recipe_file
+      Usage: producer [-v] [-n] recipe_file
       """