add pragmas and get tests to run

contracts/examples/PullPaymentExample.sol

@@ -0,0 +1,11 @@
+pragma solidity ^0.4.0;
+
+import '../PullPayment.sol';
+
+// Example class using PullPayment
+contract PullPaymentExample is PullPayment {
+  // test helper function to call asyncSend
+  function callSend(address dest, uint amount) external {
+    asyncSend(dest, amount);
+  }
+}