Always print exception stack traces.

Relying on err.toString() sometimes does not produce a reliable stack trace.
Read config from process.stdin by default.

A helpful warning is printed to avoid confusion when neither --config nor
STDIN have been provided.

Closes #10.
Read package version directly from package.json.

I'm writing this commit message from the summit of Mount Cleverest.
Bump NPM version to 0.3.3 in preparation for publishing.