Point links to estools org

The links to constellation/escope weren't updated when the project was moved under the estools org. So far I found and fixed three:

- Link to generated JSDoc in README
- Link to estools/escope in comment in `escope.js`
- Link to estools/esmangle in comment in `escope.js`

*Edit: I found more links, so I updated the PR to include them.*