Changed the keyword for emailing from 'contact' to 'email' per https://github.com/swcarpentry/styles/issues/178 and changed the description for how to use GitHub to reflect usage of the web interface.

Clarified instructions for using GitHub to contribute, altered link for [issues] to direct to GitHub page on navigating issues to avoid FIXME issue with link when initializing, removed link to master repo to avoid FIXME issue with link when initializing. These suggestions were based on a pull request initially done elsewhere swcarpentry/shell-novice#639

Close #186

Close #178

Demo at https://github.com/swcarpentry/lesson-example/pull/132/.

This is based on https://github.com/swcarpentry/lesson-example/pull/127/.

The consumer was removed by 079d7d50 (Updating contribution guidelines
in boilerplate, 2016-06-26).

1.  Renaming Ruby file to use underscore in name (consistent with other `bin` scripts).
2.  Generating `_includes/all_figures.html` for the first time when creating a new lesson.