Simplify the test runner config setup based on the test runner.

Eg. Make a "mocha" test runner preset, rather than a recipe.

As an example:

{
 "testRunner": {
        "command": "./node_modules/.bin/mocha",
        "args": {
          "filter": "--grep",
          "tap": "--reporter=mocha-tap-reporter"
        }
}

Mocha requires:

1. installed dependencies npm install mocha
2. a reporter for TAP (currently from npm install mocha-tap-reporter)
3. capture commands for filtering tests by a regex (--grep).
4. package.json script to call "mocha"

All of this could be captured in a commit, and a testRunner config.