Add support for lifecycle callbacks.

[alexandred]

Currently the only events are 'user_connect' and 'user_disconnect' which are triggered serverside whenever the user logs in or logs out. These events also trigger when the user navigates to the app with a valid session cookie or closes the window.

These events can trigger a block to run by adding the following code to a volt app:

Volt.current_app.on("user_connect") do |user_id|
# fetch user
end

Volt.current_app.on("user_disconnect") do |user_id|
# fetch user
end

[ryanstout]

@alexandred This looks great, any chance you could add some integration specs for this? (on the kitchen sink app)

[ryanstout]

the user_id cookie is encrypted and in this case will get passed as metadata since your calling UserTasks.logout before the actual logout. So you can probably just remove the arguments.

[ryanstout]

@alexandred also, What do you think about doing a 'connect'/'disconnect' events as well? (So ones for when a user connects, and one just for general anyone connects.

[alexandred]

@ryanstout i've written specs for the user_connect/user_disconnect events. i've also added general client_connect/client_disconnect events.

[ryanstout]

This should be respond_to? Would you mind updating?

[alexandred]

@ryanstout typo fixed! it's a bit late to be fixing up PRs, thought it was weird that the specs regressed :)

[ryanstout]

Nice work! Merged!