Include saltstack support within custom lxc builds

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Fix binary name for apt repository

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Append sources repository for any build-dep requirements

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Merge branch 'master' of github.com:fgrehm/vagrant-lxc into salt-feature-1
Merge pull request #116 from battlemidget/salt-feature-1

Salt feature 1