Implement arrayed sub-cadence.

Implement a sub-cadence that can be called more than once to build an
array of responses for the subsequent function.

Moved the `cadences` variable into the `invocation` structure as a
`cadence` property.

Closes #64.
Rename `emitter.t.js` to `events.t.js`.
Implement fixup cadences.

Implemented arrayed fixup cadences, completing fixup cadences.

Closes #61.
Notes on zero to many language.
Implement arrayed zero-to-many callbacks.

Also, build on Travis CI for the next few builds.

See #62.