Upgrade librarian-puppet to version 2.0.0

Upgrade librarian-puppet to the latest version, which supports Puppet
3.6 and above. This is in preparation for upgrading Puppet to version
3.7.1.
Amend SHA commitish for puppetlabs-rabbitmq module

The `strip-backslashes` branch was rebased to fix a merge conflict with
recent changes to the upstream `master` branch.

This caused `librarian-puppet` to error with:

    Could not checkout git://github.com/alphagov/puppetlabs-rabbitmq.git at 72785de752337ef050f0ec5462f96d21ac8e8ce6: fatal: reference is not a tree: 72785de752337ef050f0ec5462f96d21ac8e8ce6

Update the commitish in `Puppetfile.lock` to the tip of the rebased
branch, which resolves the above error.
Change Vagrant box; upgrades Puppet to 3.7.1

Previously, we were using these Vagrant boxes from Puppet Labs:
https://github.com/puppetlabs/puppet-vagrant-boxes

These are no longer actively maintained (last commit was two years ago)
and supply an old version of Puppet, version 3.0.2.

This commit switches to use the new Puppet Vagrant boxes built using
Packer:
https://github.com/puppetlabs/puppetlabs-packer

No URL is necessary as these boxes are downloaded from Vagrant Cloud:
https://vagrantcloud.com/puppetlabs

This also allows us to use the new Ubuntu Trusty box from Vagrant Cloud
while keeping the Puppet version consistent between Precise and Trusty.

I have tested `ci-master-1`, `ci-slave-1`, `ci-slave-2` and
`transition-logs-1` using this new Vagrant box.
Add a SATA disk interface to the Virtualbox VM

In the previous commit, we changed the Vagrant boxes we're using to the
newer ones provided by Pupppet Labs, which include Puppet 3.7.

Unfortunately the new Vagrant boxes differ from the old ones in that
they use an IDE hard disk interface, rather than SATA.

This commit creates a SATA interface in addition to the IDE interface,
which allows Vagrant to add extra disks to the `transition-logs-1` VM
correctly.

This is really a workaround until Puppet Labs use SATA for their Vagrant
boxes. I've raised a [PR] to do that.

[PR]: https://github.com/puppetlabs/puppetlabs-packer/pull/25

This was casuing the following error:

    » vagrant reload transition-logs-1
    ==> transition-logs-1: Checking if box 'puppetlabs/ubuntu-12.04-64-puppet' is up to date...
    ==> transition-logs-1: Clearing any previously set forwarded ports...
    ==> transition-logs-1: Fixed port collision for 22 => 2222. Now on port 2205.
    ==> transition-logs-1: Clearing any previously set network interfaces...
    ==> transition-logs-1: Preparing network interfaces based on configuration...
        transition-logs-1: Adapter 1: nat
        transition-logs-1: Adapter 2: hostonly
    ==> transition-logs-1: Forwarding ports...
        transition-logs-1: 22 => 2205 (adapter 1)
    ==> transition-logs-1: Running 'pre-boot' VM customizations...
    A customization command failed:

    ["storageattach", :id, "--storagectl", "IDE Controller", "--port", 2, "--device", 0, "--type", "hdd", "--medium", "transition-logs-1_extra_disk_sdc_controller_2.vdi"]

    The following error was experienced:

    for controlling VirtualBox. The command and stderr is shown below.

    Command: ["storageattach", "e9a4a9af-c6fe-47e4-8837-7669ecc8500d", "--storagectl", "IDE Controller", "--port", "2", "--device", "0", "--type", "hdd", "--medium", "transition-logs-1_extra_disk_sdc_controller_2.vdi"]

    Stderr: VBoxManage: error: The port and/or device parameter are out of range: port=2 (must be in range [0, 1]), device=0 (must be in range [0, 1])
    VBoxManage: error: Details: code NS_ERROR_INVALID_ARG (0x80070057), component StorageController, interface IStorageController, callee nsISupports
    VBoxManage: error: Context: "AttachDevice(Bstr(pszCtl).raw(), port, device, DeviceType_HardDisk, pMedium2Mount)" at line 744 of file VBoxManageStorageController.cpp
    >

    Please fix this customization and try again.