Set exit code to 1 when electric_sheep command fail
Use vagrant multi-machine capability for building packages
Move build control in package generation script
Add a wrapper on the ES executable to make the GC more aggressive

* Make the wrapper inject GC settings
* Symlink /usr/bin/electric_sheep on the wrapper instead of the
executable
* Added a build for Debian
Merge branch 'vagrant-build-enhance'

Conflicts:
	lib/electric_sheep/cli.rb
	lib/electric_sheep/runner.rb
	spec/electric_sheep/cli_spec.rb