lookupCommand now checks in addons for a command if it's not in core
extract logic to get a projects addonCommands to a method on the project
move addonCommand to a fixture to reuse it
add addon commands to help and jshint fix
pass project into lookupCommand when running cli command
update changelog
fix tests, style update
log warning when addon tries to override a core command
verify dependency package.json path exists before requiring it
Fix new command not running from cli since pkg was undefined
Group help commands output by addon
add eachAddonCommand method to Project to simplify looping over addonCommands when it's done
Merge pull request #1196 from jakecraige/feature/addon_commands

Feature: Addons add commands to the CLI