use R as base because it's trickier to set up right on Travis

hides old lesson guide

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

gold looks more like the yellow from the original badge

This contribution adds reference to the web page of the lesson in the Carpentries and makes it easier for visitors who want to contribute to get familiar with the good first issue badge.
This adds a list of current maintainers to the README.md.

Add note about title casing to style guide

Also, improve contrast of comments

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

Use the same colors but apply 12.5% opacity.

Solution boxes use 30% opacity

01-design.md: improve wording

Pull Request: carpentries/styles#388

Clarify wording of PR & issue templates

I see lots of contributions where none of this placeholder text has
been deleted, but also quite a lot where the first line has been deleted,
but the 'ext below' hasn't (exactly in accordance with the current
instructions).

links.md: lesson-specific links

06-style-guide.md: declare code block types

Pull Request: carpentries/lesson-example#225

* replace sub-heading with sub-title