add optional before parameter for adding commands
support before argument for addCommands
throw exception if before command not found; adjust code style
Add unit tests for PR #27.
Code style.
Merge pull request #1 from discordier/feature-add-commands-at-position

Add unit tests for new feature and code style
Merge pull request #27 from netzmacht/feature-add-commands-at-position

Feature: Add commands before another command.