bin/lesson_initialize.py: Remove 'example-site' reference

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

Rev 7da36a56 added a new row to the syllabus table with only 11 columns (instead of 12), which broke layout.
This fix adds the missing space.

Including mention of Library Carpentry in include files

Knit episodes only when any one RMarkdown source changes

Adding comments on purposes of include files

Using page.previous and page.next for links instead of loop

lesson.scss: 2em left padding for lists

Example of the problem: see "Ten Things You Need To Know" from http://swcarpentry.github.io/lesson-example/
For numbered lists that have more that 9 elements 1 em padding on the left is not sufficient. The result is that "1" in numbers "10" and above is printed on top of the border of encapsulating HTML block. 2 em padding solves this problem for lists with less that 100 elements. It should be safe to safe to assume that numbered lists in Carpentries' lessons should not have more than 99 items.

Starting to incorporate Library Carpentry materials

Add link to setup from schedule

Adding link to training survey to config

Adding Google Analytics code

accessibility fixes.

fix search meta tag.

Add label to search box and navigation arrows.

1. Checking that `index.md` has `root` set to '.'
2. Checking that `_config.yml` has `root` set to '..'