Automatically run dependant plugins

[markdalgleish]

I love this plugin, but felt that you need to hide the dependant plugins from the end users of this project.

Now, you can use this plugin like this:

bespoke.horizontal.from('article', {
  secondary: true
});

It might be worth updating the dependencies so that they can be run multiple times without causing errors. I'm more than happy to help with that work :)

[joelpurra]

This fix (potentially) breaks other plugins, which have convenient or indexfinger as dependencies, such as jumpy and logbook. These dependencies may currently work anyways, by chance, but they are not prepared for multiple deck activations.

I'm planning to accept this pull request, then modify it a bit. First I need to patch convenient with automatic dependency checking and activation.

Further discussion in bespoke-convenient issue #2, allow for automatic dependency checking, per deck activation.

Thanks!

[joelpurra]

@markdalgleish: thanks!