Add a script to create a fake group

This fixes https://github.com/boxen/our-boxen/issues/235 in a more permanent way
Improving echo messages

Also changed to boxen standard of "No message if nothing changes"
Merge branch 'master' of https://github.com/boxen/our-boxen into fix_gid_issue
Changed to an ask for adding to /etc/groups

Bash y/n code adapted from http://stackoverflow.com/questions/226703/how-do-i-prompt-for-input-in-a-linux-shell-script
Merge branch 'master' into fix_gid_issue

Conflicts:
	script/bootstrap
Merge pull request #581 from petems/fix_gid_issue

Add a script to create a fake group