Whitespace
Because we changed the shellwreck loader to load plugins once (for performance) the "smart" plugins like "ruby-version-manager" and "local-tunnel" which dynamically added plugins during the load process were not working because at that point, the plugin locations had already been cached.  The solution was to extract the addition of a single plugin into the __shellwreck_add_plugin function which would update the cached paths each time it's called.  Since the "smart" plugins call that method, it works correctly.
Add a PAGEKITE_PID_FILE environment variable for everyone to use
If calling pkstop when Pagekite isn't running, don't throw an error, just exit gracefully (but make sure to clean up the PID file)
Add additional pairing options for git author info
Change the default pairing email to 'pair@example.com'
Allow PAIRING_SSH_PORT to be overridden by user's local configuration
Append the global user's github username to the user_names (if the config option is set) when setting the VCS author info
Sort the user names in alphabetical order so that no matter whose system we are on, the email address will always be the same.

For example on my system, if we did not sort alphabetically, if I was pairing with blakecash, then the email would be:

pair+jfelchner-blakecash@example.com

Whereas if we were pairing on Blake's system, the email would be:

pair+blakecash-jfelchner@example.com

If we're creating Gravatars for each email, this would be double (or potentially more if we're pairing with more than one person) work, by sorting them, the email (no matter whose system we're on) is:

pair+blakecash-jfelchner@example.com
When appending the usernames to the pairing email, use Gmail's "+" email functionality to be able to use one email address with multiple usernames behind it.
Merge branch 'feature/add-smart-pairing-emails'

* feature/add-smart-pairing-emails:
  When appending the usernames to the pairing email, use Gmail's "+" email functionality to be able to use one email address with multiple usernames behind it.
  Sort the user names in alphabetical order so that no matter whose system we are on, the email address will always be the same.
  Append the global user's github username to the user_names (if the config option is set) when setting the VCS author info
  Allow PAIRING_SSH_PORT to be overridden by user's local configuration
  Change the default pairing email to 'pair@example.com'
  Add additional pairing options for git author info