Minor fixes to license file.

Validator should fail when FIXME present

Add validator target to makefile

Update validator to work with revised LICENSE.md.

1.  Remove copyright information about code of conduct (which isn't in this repo).
2.  Change ownership of trademark to NumFOCUS.
3.  Use uniform link syntax.

First should come the common workflow tasks, then commands for internal/debugging use.

Our authors use this label to mark unfinished/work in progress lessons.

Fix validation of motivation.md

Skip mailto links in link validation

Add validation for callout boxes

Implement template-specific callout rules. Add tests and fix bugs revealed.

Narrow def of callout: block must have heading.

Simplify way that callout counts are tracked, improve log messages, and add further unit tests of callout validation.

Ensure that callout validation is actually run

Set fig.path in tools/chunk-options.R to send all plots to fig/

default instead of figure/.

As per swcarpentry/lesson-template#140, but only the core CSS
changes.

Improve script to setup labels

Validator should check that required files exist

- Delete GitHub's default label that will not be used
- Create new labels
- Update color for labels

Import style for slides from https://github.com/swcarpentry/slideshows

Excluding unwanted files from build

Change filters since classes must be explicit

Improving support for R Markdown.

1.  Adding `tools/chunk-options.R` with support for Pandoc-based conversion of R Markdown to plain Markdown.
2.  Modifying `Makefile` to handle any R Markdown files that are present.

Changes have been checked by @jdblischak in the `r-novice-inflammation` project.

Small improvements to CSS