General New User Umbrealla Issue

[Olshansk]

I'm hoping to keep this "issue" to discuss a few general questions/suggestions as I'm getting acquainted with the library. I'm happy to contribute as well, but wanted to get some feedback first before putting together a formal PRt.

Regarding the Signers interface:

1. Why not put the types directory under test/types given that it's used for testing?
2. What's the motivation between only having one owner and one other rather than a few (or a list?) of users?

Regarding tests: 3. I was thinking of adding a few examples of different tests for future readers, but not sure if that's outside the scope of this github repo in terms of what you had in mind.