tests: Updating tests to have correct include path for ndn-js

Now all test cases include ndn-js.js directly.  Helper.js has been
removed from the source.

Status:
 - there is some problem with tests/test-PIT-matching.html
   In Chrome it complains about missing to_ccnb call on Object,
   In Firefox it is doing something, but not everything
diff --git a/tests/test-signature-string.html b/tests/test-signature-string.html
index 025d065..0d0cab6 100644
--- a/tests/test-signature-string.html
+++ b/tests/test-signature-string.html
@@ -9,7 +9,7 @@
 <head>

 	<title>NDN Signature - String</title>

 

-    <script type="text/javascript" src="../Helper.js"></script>

+    <script type="text/javascript" src="../build/ndn-js.js"></script>

 		

 	<script type="text/javascript">

 		function sign(){