implement bracketed paste mode (fixes #56)
start working on tracking selections
function to get a stringified version of a screen region
basic implementation of selections

still need to draw the selection, and look into how selections persist
after the application is closed (cut buffers?)
row has already been offset properly
also respond to TARGETS requests
simplify
allow backwards selections
store this on the screen
draw the selected region as inverse
rearrange
update the selection as the mouse move
display selection past the end of a row properly
more fixups to selection past the end of a row
clear the selection when the window is resized