fixed XHRHelper get basePath error
fixed XHRHelper get basePath error

ie: root=x-wmapp0:xface\\helloxface\\index.html;
var basePath = root.substr(0,root.lastIndexOf('/')) + '/';
get basePath will error.
we should  replace "\\"  with "/" before  get basepath

polyvi/xface-wp8,polyvi/xface-wp8,polyvi/xface-wp8