Brightnessctl

* Added a `--min-value` option to set a minimum allowed value for brightness decreases (thanks taingra)
* Minor refactoring

Added a manpage, thanks nbraud, SirCmpwn

* Fixed build on some older debian systems (specify `-lm` the correct way)
* Allow device names to be specified by a wildcard (e.g. `brightnessctl -d "*capslock"`)

Note: this release has some changes in install process. Please review the Makefile for more info.

* Prevented code from using non-standard GNU extensions
* Added a `--version` flag (christophgysin)
* Added a `info` operation (renamed from `get`, which extracts only the current brightness now) (hcpl)
* Fixed a rounding error with percentages (modernrio)
* Added an option to automatically install udev rules (christophgysin, Miciah)
* Modified the install process to respect DESTDIR/PREFIX conventions.

Fixed several logic errors.

- Extended documentation (thanks to Fale)
- Allowed to use sign in prefix (e.g. `+5%` in addition to `5%+`)
- Root privileges are no longer required (write permissions are enough, details are in the README)

Huge thanks to Miciah for fixing a number of bugs:
- A buffer overflow in `cat_with()`
- Making saving state work from the first try
- Enforcing additional runtime constraints
- Detalising and expanding error handling


0.1.1_p2
- Licensed to MIT
- Made first found device the default one
- Fixed write on older kernel versions
- Fixed the makefile