Added CoreOS task to Razor.

Allowing for full clusters of CoreOS to be deployed, automatically
configuring the setup with heavy use of Razor's node-metadata function to
enable features like etcd configuration, fleet metadata, formatting of
drives and automatic addition of SSH keys. Since the node-metadata is
applied on all nodes, their value can easily be updated with different
settings on a per-node basis if wanted.
Spec tests for `razor events`

This adds tests for the `razor events` query.

For https://tickets.puppetlabs.com/browse/RAZOR-382
Limit results from `razor events`

The list of events in `razor events` can grow unwieldy very quickly. This
change instates a default of all rows returned with options to return
different rows using parameters /api/collections/events:
- `limit` determines the maximum number of rows to return,
which defaults to 20.
- `start` determines what row number to start with, which defaults to 0.

This includes both of these parameters in `/api` under
`collections => events => params`.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-382