Add notifications

[calavera]

- Do you want to request a feature or report a bug?

This is a new feature.

- What is the current behavior?

There is no way to notify people.

- If the current behavior is a bug, please provide the steps to reproduce.

- What is the expected behavior?

People should be able to subscribe to changes in the status page.
We can use services like chimpmail and twilio that provider JS api's for this. We can also use some Lambda functions for more elaborated notifications if we need to.

Minimum services I'd like to integrate with:

• Twitter
• Email
• SMS