More useful & friendly status output

[paigeruten]

leg status should tell you more about the tutorial, like the total number of steps it has and the actual step number of the last step when it is checked out. It should not only tell you the state your working directory is in, but enumerate all the possible actions you may want to take from that point with actual examples of what leg commands to run to take those actions (like git). Some commands should automatically show similar status messages, such as when you commit and get a conflict that needs to be resolved.