callback javascript errors instead of objects (#303)

Author: revington

lib/nano.js

@@ -137,11 +137,9 @@ module.exports = exports = function dbScope (cfg) {
         reject(new Error(`error happened in your connection. Reason: ${response.message}`))
       }
       if (callback) {
-        const returnError = {
-          message: `error happened in your connection. Reason: ${response.message}`,
-          scope: 'socket',
-          errid: 'request'
-        }
+        const returnError = new Error(`error happened in your connection. Reason: ${response.message}`)
+        returnError.scope = 'socket'
+        returnError.errid = 'request'
         callback(returnError)
       }
       return