.gitconfig: Add default Git `push.default` config

Use the backwards-compatible `matching` setting by default. On machines with newer Git installations, it avoids the annoying Git warning, and it can be overriden to use `simple` instead in `~/.extra`.

Closes #400.
Add `.editorconfig`

See <http://editorconfig.org/>.
.bash_prompt: Avoid double-escaping ANSI codes

Fixes #399 and closes #402.
Added add-commit shortcut
Merge commit '3ec5769e54aaf23c07ef7beca180db698306d808'

* commit '3ec5769e54aaf23c07ef7beca180db698306d808':
  .bash_prompt: Avoid double-escaping ANSI codes
  Add `.editorconfig`
  .gitconfig: Add default Git `push.default` config

Conflicts:
	.bash_prompt