adding page tracking analytics

README: Update 'r-gaia-cs' -> 'rgaiacs'

I thought the hyphenated form was current when I used it in 0d8da61e
(README.md: Add local maintainer listing, 2015-04-15, #2), but GitHub
no longer recognizes the hyphenated form.  The un-hyphenated form
seems to date back to 2012-03-06 [1], so maybe I was just confused ;).
Anyhow, fixing to use the current username.

[1]: https://github.com/rgaiacs

Update JavaScript locations to avoid errors

README needs to be created from scratch.

Add MathJax

Instructions on changing the URL linked to the "Source" button

Add support for error class for R Markdown generated lessons

or an error has the class "error" and appears in red font.

https://github.com/swcarpentry/lesson-example/blob/gh-pages/LAYOUT.md#topics

Fix a typo in README.md

[fix #270] check knitr version before converting Rmd to md

Removed lingering references to motivation.md and motivation.html

Removing Legend from required headings

Removing motivational slideshow

Removing support for motivational slideshows

Merge branch 'removing-motivational-slideshow' of github.com:gvwilson/lesson-template into removing-motivational-slideshow

on a suggestion of @sritchie73 and @aammd

Avoid wrong error with links at index.md

Clarifying challenge format

Modifying page template so that main title links to home page.