Small bug fixes
Modularized guitree creation in the layout

This way it's possible to customize manipulating the tree.
E.g. imitating tile or fair from awful.
Improved container labelling when using select_node, still needs tweaking
Tweaked behavior when removing nodes
Added more options when manipulating selected containers

Also renamed attributes
Updated keybindings and added keybinding wrapper
 Added layouts, fixed bugs, updated keybindings

 See updated README