Merge branch 'master' into develop

Conflicts:
	Gemfile
	lib/tracking/cli.rb
	lib/tracking/config.rb
	lib/tracking/list.rb
	lib/tracking/task.rb
	spec/config_spec.rb
Readme: Tell users to keep Ruby up to date instead of hinting at 1.8.x support
Merge branch 'master' into develop
Merge branch 'develop' into feature/terminal-table