Add bootstrap style alert messages

[clburlison]

This PR add bootstrap style alert messages. To make an alert you use one of the following:

{{% alert success %}} Here's a success... {{% /alert %}}

{{% alert info %}} Here's a info... {{% /alert %}}

{{% alert warning %}} Here's a warning... {{% /alert %}}

{{% alert danger %}} Here's a danger... {{% /alert %}}

As it stands, I'm not sure where best it would be to document this? Or if I inserted the css in the ideal location?

[enten]

Awesome works! Thanks a lot sir.