Add release method to Stoppable. Create StoppableMock

contracts/test-helpers/StoppableMock.sol

@@ -0,0 +1,17 @@
+pragma solidity ^0.4.0;
+import '../Stoppable.sol';
+
+// mock class using Stoppable
+contract StoppableMock is Stoppable {
+  bool public drasticMeasureTaken;
+  uint public count = 0;
+
+  function normalProcess() external stopInEmergency {
+    count++;
+  }
+
+  function drasticMeasure() external onlyInEmergency {
+    drasticMeasureTaken = true;
+  }
+
+}