Dumptruck-related additions

The two command additions here are:

* `apps:create`, for creating a new OpsWorks app.
* `recipes:add`, for adding a recipe to a given layer and lifecycle event.

The workflow for adding and deploying a new app now goes something like this:

1. Commit, release and deploy a new Chef recipe to perform the deploy (say, `aptible::newapp`).
1. Update any security group rules for the new app.
1. `opsworks apps:create newapp`
1. `opsworks recipes:add master deploy aptible::newapp`
1. `opsworks apps:deploy newapp`

In addition, I've renamed most of the commands to group them under "namespaces," for cleaner module organization and a friendlier interface. As a result, the minor version needs a bump.

* `deploy` :arrow_right: `apps:deploy`
* `status` :arrow_right: `apps:status`
* `allow` :arrow_right: `iam:allow`
* `lockdown` :arrow_right: `iam:lockdown`
* `exec` :arrow_right: `recipes:run`