Doesn't work with latest Dart and Spectre

[markhats]

Doesn't seem to work with Dart M4 and the latest version of Spectre from Git. Fixed quite a few issues regarding changes in Dart but still lot's of "NoSuchMethodError" errors related to Spectre, I think.

[donny-dont]

Hey @markhats. I'm actually in the process of moving this code into the core Spectre. There's definitely been some bit rot on my end with this demo.

You can see some of this landing at https://github.com/johnmccutchan/spectre/pull/56