Add some explanation

Hey Ed - I had to look up "Cognitive Behavior Therapy tool". I don't think I'm qualified to do a PR for this, but perhaps in the README, you could add a brief paragraph on what one is for, what yours does, etc. I saw some articles and tools, but I wouldn't know enough to recognize a good resource, other than maybe the Wikipedia definition (http://en.wikipedia.org/wiki/Cognitive_behavioral_therapy).

Start by reading the README and compare its current description with the issue's request. Use the linked Wikipedia definition as a possible reference, while explaining what Cognitive Behavior Therapy tools are for and what this web-based tool does. Done means the README contains a brief, understandable introductory paragraph.

Written by the indexing model from the issue text.