Append "Behavior" to "BootstrapValidator" for consistency-sake

When I wanted to add the `BootstrapValidator` behavior into a new project, I noticed that I made an mistake in the `index.js` file and define the behavior with a different name syntax. It was missing a `-Behavior` at the end.

So for the sake of consistency, here is it. I also took the liberty to add some usage documentation.

:v: