Fix - add missing support for passing SQL stmt via msg.topic (#21)

* Fix - add missing support for passing SQL stmt via msg.topic

Support for this functionality is documented in alasql.html "<p>The <code>msg.topic</code> can hold several SQL queries separated by <code>"

* Change the order from what source read a SQL query

node-red-contrib-alasql.js

@@ -6,7 +6,7 @@ module.exports = function (RED) {
         var node = this;
         node.query = config.query;
         node.on("input", function (msg) {
-            var sql = this.query || 'SELECT * FROM ?';
+            var sql = this.query || msg.topic || 'SELECT * FROM ?';
             var bind = Array.isArray(msg.payload) ? msg.payload : [msg.payload];
             alasql.promise(sql, bind)
                 .then(function (res) {