Upgrade node environment to Node.js 7.6.0+ (#151)

Upgrades the node environment to NodeJS 7.6.0.  Functions can now use async/await and promises; they can return a promise instead of using a callback.  The change preserves compatibility with the callback style.  

* Upgrade node environment to Node.js 7.6.0+

* Bump package version

* Preserve compatibility for callbacks

* Cleanup

* Re-add hello callback example

* Make sure not returning won't blow everything up

* Update stock example with request promise

environments/nodejs/server.js

@@ -75,11 +75,13 @@ app.all('/', function (req, res) {
         res.status(500).send("Generic container: no requests supported");
         return;
     }
+
     const context = {
         request: req,
         response: res
         // TODO: context should also have: URL template params, query string
     };
+
     function callback(status, body, headers) {
         if (!status)
             return;
@@ -90,18 +92,32 @@ app.all('/', function (req, res) {
         }
         res.status(status).send(body);
     }
-    try {
-        //
-        // Customizing the request context
-        //
-        // If you want to modify the context to add anything to it,
-        // you can do that here by adding properties to the context.
-        //
-        userFunction(context, callback);
-    } catch(e) {
-        console.log(`Function error: ${e}`);
-        callback(500, "Internal server error")
+
+    //
+    // Customizing the request context
+    //
+    // If you want to modify the context to add anything to it,
+    // you can do that here by adding properties to the context.
+    //
+
+    let functionProm;
+    if (userFunction.length === 1) { // One argument (context)
+        // Make sure their function returns a promise
+        Promise.resolve(userFunction(context)).then(function({ status, body, headers }) {
+            callback(status, body, headers);
+        }).catch(function(err) {
+            console.log(`Function error: ${e}`);
+            callback(500, "Internal server error");
+        });
+    } else { // 2 arguments (context, callback)
+        try {
+            userFunction(context, callback);
+        } catch (err) {
+            console.log(`Function error: ${e}`);
+            callback(500, "Internal server error");
+        }
     }
+
 });
 
 app.listen(argv.port);