Open in Colab URL broken in 0.1.1

[adamjstewart]

The latest 0.1.1 release broke the "Open in Colab" URL in our tutorials. Still trying to fix this.

[adamjstewart]

There are two issues here:

1. The URL format is broken, contains a literal {{ env.config.version }} instead of the expansion
2. Even if 1 worked, the docs for the latest version would try to clone from releases/v0.2 which does not yet exist

I think we can check for 2 by seeing if this is a .dev0 release.