Add type properties to hooks

[tcoats]

AttributeHook has a type property available on it's prototype but the other hooks don't. Providing the type property helps other libraries parse vdom, such as this discussion in vdom-to-html. At the moment there is no easy way to convert a hook to html. Using instanceof requires the same npm package which isn't always possible.

This PR adds a type property to ev-hook, focus-hook and soft-set-hook.

If it makes sense it might also be nice to add corresponding is-ev-hook, is-focus-hook and is-soft-set-hook files in vnode.

Thoughts?

[coveralls]

Coverage increased (+0.01%) to 97.5% when pulling 4653975 on odojs:hook-to-html into 88534bb on Matt-Esch:master.

[kuraga]

See also #248

[DeTeam]

@tcoats what do you think about having .toString on hook's prototype?

[TimBeyer]

I think @DeTeam has the better proposal here.
That way html conversion behavior is defined by whoever defines a hook and elegantly solved by polymorphism instead of starting to switch on some kind of type identifier.
This would solve the issue completely for the future.

[tcoats]

@DeTeam I think it's great!

The only drawback is that each component will need to include a stringify library - but the freedom string gives over vdom is excellent.

[DeTeam]

The only drawback is that each component will need to include a stringify library

@tcoats, not really :) it's all about being able to represent Hook as a string. vdom-to-html lib can't guess on how to do it. If we go with just using hook.value it doesn't fix user hooks, while having something like toString, render as part of Hook interface will allow custom hooks to be automatically handled by vdom-to-html.

[tcoats]

@DeTeam In my case I'll probably need to use a stringify lib more if toString is added to widgets as well, which I think is a great idea. Should toString be added to widgets?

toString is an excellent and useful addition!