Deploy new incremental tester

I think we're good to go on this one

It got a little out of hand: it now resembles a bare-metal TSD :see_no_evil:

Commits are pretty involved as it went through a few stages (refactor forever, see commit history for dirty details). I could flatten it oc.

Most of old test code still exists, only re-factored, wrapped in Promises and with a fancy pre-phase to select files. 

Main things it does:

1. index all .ts files
2. parse references
3. get git diff changes
4. intersect diff and index
5. bail if index has files that refer to removals
6. recursively solve references to changed files
7. pass all involved files to existing test suite runner
8. run tests but on less files
9. :sparkles::smile_cat::sparkles:

You can make definition PR's against `stage/tester` branch to test it and see it in action (or test  your own fork if you have travis enabled). Also this git command works in a local checkout (as long as you don't commit, but we can solve that later).

Known issues:

1. Doesn't parse for `import` yet. I saw no content using it currently, but should be easy to add.

Please send feedback or an OK to merge (this weekend).

Closes #1314