Added boxen upgrade instructions
Added more detailed update process
Moved Upgrading instructions to FAQ
fixed spelling error
Update README.md

Other boxem fixed.
Merge pull request #587 from nbmorgan/master

Added boxen upgrade instructions
Upgrade puppet-git to 2.3.1

Closes #598
Merge branch 'refs/heads/our-boxen/master'
Removed Puppetfile.lock from .gitignore.

This is included within our-boxen just like the Gemfile.lock module, and is probable safe to include in this branch as well.
Updated Puppet modules and Ruby Gems.

This has been done according to the update instructions from the FAQ.