Add back in usage/example to alfred:list

[kcmerrill]

I didn't think it was necessary which is why I didn't add it in to the latest version, but I think we need it.

Not only usage text for each task, but an example.

tdd:
   usage: alfred /testing:tdd <reg_expression> <command_to_execute_on_file_change> 
   example: alfred /testing:tdd ".*?.go$" "echo something here"