update info on formative assessments

jekyll version

Add note about version of Jekyll needed per https://github.com/swcarpentry/styles/issues/195#issuecomment-351056899.

fixed broken link on landing page

Fix link to setup page in index

Add Library Carpentry website to _config.yml

Close #150

Close #152.

Per _config.yml in workshop-template, adding Library Carpentry website info for appropriate linking in _includes/lesson_footer.html

The link to setup is broken. This pull request suggest to link to the existing setup page (`{{ page.root}}/setup.html`), but other options are 
 to change the permalink on Setup to `{{ site.url }}/setup/`

Syntax highlighting example

Syntax highlight

Based on https://github.com/swcarpentry/lesson-example/pull/144/files

Close https://github.com/swcarpentry/lesson-example/issues/145.

Close #186

Close #140

Use email as keyword

Adopt email instead of contact as keyword