Metacello: Update to Latest in Load Scripts

[seandenigris]

I think it's required for e.g. bitbucket://:

Metacello new
  baseline: 'Metacello';
  repository: 'github://dalehenrich/metacello-work:master/repository';
  get.
Metacello new
  baseline: 'Metacello';
  repository: 'github://dalehenrich/metacello-work:master/repository';
  onConflict: [:ex | ex allow];
  load.

But Metacello does not support bitbucket:// et al via SSH keys, so keep on hold for now.