Add course content to repo

[annechenette]

This version of the course includes:

• Creative Commons (CC BY 4.0) license on the front page of each module
• Clarification in module 1 that ZMQ is helpful but not required
• Correction for a typo in module 3.

NOTE: This PR supersedes #21.

Signed-off-by: Anne Chenette chenette@bitwise.io

[annechenette]

Closing PR. I will open another that's on the correct source branch and includes the license statement in README.md. Please see PR #23.