`L` moves to count line from bottom of viewport
`L` will move to count line from bottom of file when file is shorter
`L` will not move above the top of the viewport
`H` moves to the count line on the screen
`H` will not move below the bottom of the viewport
Rename defhandler -> mapkey
:keep-count? -> :keep-count, :no-repeat? -> :no-repeat
mapkey can bind repeat count and assumes :no-repeat
Note that we need a curses to install.

Closes #7