Changes:
  * Expand button_scan to be able to monitor a full USBMS session, detecting content import in the process (#11)
  * Add support for infinite progress bars, via the -A, --activitybar flag, for tasks of indeterminate duration (#12)
  * Handle the native viewport on Kobo devices with rows of pixels hidden by a bezel (#14)
    Currently only enabled on the H2O, despite being applicable to the Aura (quite definitely), and possibly the H2O²
    Send me fbgrab snapshots from inside nickel to change that ;)
  * Make an effort to make row 0 usable, by applying a vertical shift to rows when we can't perfectly fit a final row on screen

API Changes:
  * Add fbink_get_state(), giving you access to a few internal state variables, via the new FBInkState struct (#13)
  * Add the no_viewport field to FBInkConfig, to disable any & all viewport trickery introduced in this release
    * Add it to the list of fields that affect fbink_init()'s behavior
    * Speaking of, update that list in the docs (it was missing fb_color & bg_color)
  * Add fbink_print_activity_bar(), to draw so-called "infinite" progress bars
  * Add fbink_wait_for_usbms_processing(), to monitor Kobo USBMS sessions, faked or otherwise.