Add --with-ids option

`--with-ids` can be specified on listing of images, regions, sizes and snapshots.
This is a convenience for tools like Packer, which use these IDs.

This will be in the next release, but if you want to use it in the mean time, install pontoon from master like so:

```
pip install git+git://github.com/duggan/pontoon.git#egg=pontoon
```