Implement basic `sh' task action feature:

* Executes a command on the remote host;
* Forwards remote standard output.

features/actions/sh.feature

@@ -0,0 +1,26 @@
+@sshd
+Feature: sh task action
+
+  Scenario: executes command
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :some_task do
+        sh '\true'
+      end
+      """
+    When I execute the recipe
+    Then the exit status must be 0
+
+  Scenario: forwards standard ouput
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :some_task do
+        sh '\echo from remote'
+      end
+      """
+    When I execute the recipe
+    Then the output must contain "from remote"