Modernize README using Markdown

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Fix: utils/run.sh: use `echo -e` to interpret \n

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Sort list of directories in run.sh scripts

This mimics the behaviour of Bash's `*/`, which is to
sort the results. Tests are executed in a deterministic
order.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
utils/run.sh: use $(find ...) instead of `*/`

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>