femto text editor

based on nano.

draws graphics using ANSI control sequences.

this means the terminal must be in raw mode with echo
turned off. the `femto` wrapper script achieves this
using `sttry raw -echo` (it also restores the previous
terminal settings on exit).

current status:
 - hardcoded input path
 - can't save changes
 - no page up/down
 - at least one delete bug
 - doesn't support long lines/horizontal scrolling
 - no search (or search&replace)
 - no help messages/status bar context
 - hardcodes 80x24 dimensions even on larger terminals

special key bindings
 C-a   go to beginning of line
 C-b   move back one character
 C-d   delete
 C-e   go to end of line
 C-f   move forward one character
 C-n   move down one line
 C-p   move up one line
 C-x   quit