README: update `ENABLE_SYSTEMD` documentation

Signed-off-by: Antoine Damhet <antoine.damhet@lse.epita.fr>

Version bump to 0.5

Version bump to 0.4

Revert manpage changes

Release 0.3.1

Use BINDIR in Makefile install rule

Fix logical errors

Restore device data only after successful read

Do not set curr_brightness to max after an unsuccessful restore

Fix ensure_dir

Do not ignore ignore value of fread (fixes #6)

Version bump

Specify year and name in the license

Updated makefile