Add support for the _COMPTON_SHADOW atom
New messages: 'drop_to{,monitor}'

'send_to' was broken, '--next' and '--prev' can't be options, and I
don't want to restrain the name of the desktops with 'send_to
DESKTOP_NAME|next|prev [--follow]' or handle multiple options: 'send_to
(DESKTOP_NAME|(next|prev --relative)) [--follow]' so I just created new
messages.
Update TODO
Show libraries
Merge branch 'master' into compton-shadow
Only floating windows needs shadow
Only highlight the option as code

We follow Tim Pope's advice:
https://github.com/tpope/vim-markdown/issues/30
Merge branch 'master' into compton-shadow
New setting: 'apply_shadow_property'

Will not have any effect unless `compton` is started with the
`--respect-prop-shadow` option.
Actually honour 'apply_shadow_property'
Don't alter the floating state of fullscreen windows
Prevent pointer actions on fullscreen windows
Check the initialization of EWMH atoms
Update TODO
Add tiled move/resize pointer actions

New arguments for `grab_pointer`: `{move,resize}_tiled`.
New setting: `fence_grip`.