Fix bug with several paperscripts loading remotely

The thing is when using multiple remote scripts, closure that evaluates script after http requestcomplete tries to access mutable variable "scope". The result is both paper-scripts will be rendered into latest scope/canvas, in example below it will be "card-back".

<script src="{{ STATIC_PREFIX }}js/paper-full.js" type="text/javascript"></script>
<script src="{{ STATIC_PREFIX }}js/postcard_front.js" type="text/paperscript" canvas="card-front"></script>
<script src="{{ STATIC_PREFIX }}js/postcard_back.js" type="text/paperscript" canvas="card-back"></script>