Improve wording on syllabus.html

As suggested by @gcapes.

Revert "ensure dt elements have an id set"

Numbering the lessons in the schedule

Related with https://github.com/swcarpentry/styles/issues/80.

Edit on GitHub

Jekyll doesn't export the _episodes_rmd so we need to flag the files.
Each Rmd file must have in the YAML header

    source: Rmd

https://github.com/swcarpentry/lesson-example/pull/104#issuecomment-283310978

Update copyright year with current year

Improve round corners on block input and output

Make tables wider

Close https://github.com/swcarpentry/styles/issues/101.

ensure dt elements have an id set

Fix layout of syllabus table

Adding JQuery debugging

Visually separate inline code blocks

Checking consolidated links

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