Run tasks by name

[ruyadorno]

It may seem counter intuitive but during some discussions in the npm cli I realized there's def a value to be provided to ntl users by allowing usage of positional arguments in order to run a task without the need of the interactive interface.

For one, it's an elegant way to fix the forwarding of arguments as described in #66 and it will also provide a nice shortcut alternative to npm run, e.g:

ntl build --with-flags -> npm run build -- --with-flags