Fix help message on wrong calls

This fixes the display of usage information when the program is called
without arguments.
Add automatic set-up script

This adds a command-line option `--init` to `jsdoctest`'s command-line
interface meant to aid users add this to their project. There's now a
one-liner (almost) which sets users up.
Add basic documentation for the `init` command

This adds a `Set-up` section to the README. It also bumps version to
1.1.0 and republishes.