Write a tutorial!

[robertdfrench]

We are doing a moderately good job documenting the code, and we have plans (#29) to write reference documentation for each individual command, but nothing beats a good overall tutorial with usage examples.

[robertdfrench]

This is sortof addressed in #58, since the man page has an EXAMPLES section, but there really should be a more extensive, preferably web-based tutorial. Likely in markdown, possibly in the top-level README.md