Add return statements for promises to fix Bluebird errors.

Fixes: #285

Author: Cody Lundquist

lib/pool.js

@@ -96,7 +96,7 @@ Pool.prototype.getConnection = function() {
     }
 
     if (self._slowGrowth === false) {
-      self._expandBuffer();
+      return self._expandBuffer();
     }
 
   });
@@ -318,7 +318,7 @@ Pool.prototype._expandBuffer = function() {
   if ((this._draining === false) &&
       (this._pool.getLength() < this.options.buffer+this._localhostToDrain) &&
       (this._numConnections < this.options.max+this._localhostToDrain)) {
-    this.createConnection();
+    return this.createConnection();
   }
 }