Don't create pipes for `P.spawn` by default.

Pipes will block if they get enough input, and our users are not
listening to the pipe (we're not even exposing it to the caller).

Change-Id: I0e6247bfbee1b1eb67441f21d39c107e4806bc01
Update dependencies.

* `commander` to 2.5.0
* `es6-shim` to 0.20.2
* `prfun` to 1.0.1
* `jshint` to 2.5.0 (and jshint added to `npm test`)
* `gammalatex` to 0.0.8 (our changes are now upstream)
* `mocha` to 2.0.1

Change-Id: I1fbd8df8e3150738a9de39b1cdaf5e67b98669e6