Add algorithms for distance and angle between two Cartesian coordinates
Expose thumbnail rectangle through interface
Methods for deciding whether a thumbnail lies in the right direction
Find closest thumbnail in given direction
Implement methods for choosing east (right), west (left), north (top), south (bottom) thumbnail
Use keys in client chooser for directional choosing of client
Rename variable to something more apt
Improve call locations of update() and reset()

Not every call to update() requires a call to reset().
The call to update() in the c'tor is superfluous since a call to
update() is made on show().
Calls to update() and reset() for _NET_CLIENT_LIST_STACKING property
notify events are only necessary when the thumbnails are currently
shown.
All this eliminates the to check for the _active flag in update() and
reset().
Implement weighting for different angles to improve matches
Revert "Implement weighting for different angles to improve matches"

This reverts commit 2b731ec7aa655073e27232bd3d4e36c66d50f1ff.

This was not a good idea.
Revert to 45° angles again
Initial README file
Improve Makefile

* Remove unnecessary library dependency
* Speed up re-compilation
Add root window as send event window member

Necessary for the request to work. Some wms might ignore the message
when the window member is unset or not root.
Rewrite method for retrieving current desktop on a window
Update the _NET_CURRENT_DESKTOP when the atom changes
Retrieve, transform & store _NET_WM_ICON

Transforming the image to ARGB (32bit) pixmap is necessary for OpenGL.
Retrieve, transform & store icon from WM_HINTS

Although this looks easy, guess why I screamed bloody murder while
implementing this.
Hint: Always use {put,get}pixel with xcb_image_t!
Retrieve & store textual window properties: {NET_,}WM_NAME, class & instance name
Free name_window_pixmap in d'tor