lxc-template: add parameter strip-components, as not all tarballs are created like ./rootfs/...
Add check for box updates to start action

This action apparently needs to be added to every provider. See
lib/vagrant/plugins/providers/virtualbox/action.rb from the Vagrant
source for reference how the virtualbox provider is doing it.
Merge pull request #314 from fpletz/fix/box-update-check

Add check for box updates to start action
Merge pull request #311 from postster/postster/tarball-strip-components-option

lxc-template: add parameter strip-components
Update changelog
Remove version suffix from generated sudoers commands
Update README
:bomb: post install message
synced_folder: Emit `vagrant-mounted` upstart event when starting containers

Closes GH-302
:fireworks: v1.0.0 :fireworks: