Set up Guard with RSpec plugin
Update travis-build
[WIP] Writing BlueBox specs

Not clear why #allow_any_instance_of is undefined.
[WIP] Use mocha instead of rspec-mock syntax
Update thor to a more recent version
Add guard-bundler
Manage Blue Box templates with Template class

Here, we introduce a wrapper class, `Travis::Worker::VirtualMachine::BlueBox::Template`,
around the Blue Box templates.

It will have useful properties (`dist`, `group`, `template`) based on the description,
so that the template can be chosen more easily than looking at description directly.