Merge tag '0.1.4'

index.js

@@ -77,6 +77,7 @@ DB.prototype.execute = function (query, params) {
       con.execute(query, params, function (err) {
         if (err) {
           if (con) {
+            con.unprepare(query);
             con.release();
           }
 
@@ -84,6 +85,7 @@ DB.prototype.execute = function (query, params) {
         }
 
         resolve([].splice.call(arguments, 1));
+        con.unprepare(query);
         con.release();
       });
     });