Added improved error message when mongo connection fails.

lib/adapter.js

@@ -8,6 +8,8 @@ var Collection = require('./collection');
 var Errors = require('waterline-errors').adapter;
 var ObjectId = require('mongodb').ObjectID;
 var _runJoins = require('waterline-cursor');
+var util = require('util');
+
 
 module.exports = (function() {
 
@@ -88,8 +90,16 @@ module.exports = (function() {
       };
 
       // Create a new active connection
-      new Connection(connection, function(err, db) {
-        if(err) return cb(err);
+      new Connection(connection, function(_err, db) {
+
+        if(_err) {
+          return cb((function _createError(){
+            var msg = util.format('Failed to connect to MongoDB.  Are you sure your configured Mongo instance is running?\n Error details:\n%s', util.inspect(_err, false, null));
+            var err = new Error(msg);
+            err.originalError = _err;
+            return err;
+          })());
+        }
         connections[connection.identity].connection = db;
 
         // Build up a registry of collections