Resolve #116: Resize signature size

[JeanJoeris]

Resolves #116 Add resizing of signatures on volunteer signature report page. We ended up just solving this with html because it made for a more explicit test. We can do this with css if you'd like though.

The signature in the shift_event factory seemed to be broken, so we added a different signature. If there is another image you'd like the factory to use, please send us that image.

[bjmllr]

Thank you!

I think the problem with the original example png was the %E2%80%A6%E2%80%A6 at the end. I guess that's a couple of ellipsis. Does it work if you remove that?

[JeanJoeris]

That fix the image. I went ahead squashed the commits.