Using `.spread` gives error on error

[lapo-luchini]

Seems like err.response can be written to.

TypeError: Cannot assign to read only property 'response' of 
    at Request.<anonymous> (/home/...myproj/node_modules/restler-q/lib/restler-q.js:17:29)
    at Request.emit (events.js:110:17)
    at ...