File locking - I naivly assumed that if a file is opened for
writing, unix would lock it so other programs could not write
to it. This does not appear to be the case.
    
There are other things that could be added, but I'm not
really planning to, as it would start getting too complicated
and this was only meant to be a quick-n-dirty editor.

 - Replace
 - Toggle whether file is treated as signed or unsigned chars.
 - Create new files rather than just edit existing files.
 - Alter size of file being edited (ie. insert/delete characters).
 - Cut/Copy/Paste
 - Undo
 - Config (~/.shedrc) to set things like hex mode by default.m