Complete WorkflowOp map.
Add a join test.
[minor] Formatting cleanup.
fix indent in generated JS
handle MapReduceTask in RenderTree
also a RenderTree[Js] instance
ignore ^D in REPL ('exit' still works)
Merge pull request #259 from sellout/joins

Joins
fix white space in tests
Merge pull request #260 from mossprescott/misc

A handful of small fixes
[minor] Extract a few map/reduce patterns.
Restore an error that I hid while debugging.
Fix a `merge` case that could toss req. fields.

Unfortunately, I’ve only seen this exhibited in `pending` tests that were failing differently than they should have been failing.
Merge pull request #262 from sellout/more-minor-fixes

More minor fixes