tmux pane features for focus and errors

command that removes the errorfile and restarts output capturing

pane options focus_on_restore and focus_on_make
fix: was deactivating async in the augroup instead of the exit hook
add riml and guard gems
remove duplicate 'maque: ' tags on warnings
toggle function for dummy pane
add layouts

layouts control pane creation when multiple panes should be stacked
inside of another split
Guardfile for compiling riml sources
remote vim command

add a special variant of command that provides a remote interface to a
vim instance via +clientserver functionality.
use vimproc for blocking calls, too

as starting a shell is unnecessary and slow, vimproc#system can replace
the builtin system()
don't use pipes for riml io
don't add panes and commands in remote vims
subclass pane for specialised vim pane

add VimPane class that determines vim's pane id lazily by comparing tmux
pane pids with getpid().
enable tmux pane cache for toggle()
use maque#util#system for all command executions
cache more tmux data, more structured

when caching in tmux#pane#all(), read all values that any function
using 'list-panes' needs and store them as dicts for each pane.
add pane.set_size() to apply after layout changes
use abort for functions
set the variable 'g:maque_remote' in remote vims
prepare for migration to riml
add source dirs to riml call