SSD Customizations & More Applications

* Add SSD mount option optimizations to the root partition.
* Add the YouCompleteMe vim plugin to prevent manual compilation.
* Add some additional applications and libraries: ffmpeg, taskwarrior,
  mcomix, cpupower, postgresql, unclutter and unzip.

* Modify the root label from molly_root to nixos_usb.
* Modify filesystems to mount a tmpfs on /tmp.

* Replace wicd with WPA supplicant.
* Replace the proprietary ATI video driver with the free version.