Add a NewStringSet() function

Also beef up tests to cover len(ss).
Merge pull request #289 from thockin/cleanups

Add a NewStringSet() function
Add a link to the I/O talk on YouTube
Fix the link.
Move scheduler to own package.
Fix up usage and tests, split into multiple files.

Doing this in multiple commits in an attempt to preserve the file movement history.
Add crash handler bypass for testing.