Better undo fix

The original undo fix was to make the command not a view command (because that effected the undo) but that made it too slow and needed to be called in a timeout delay which cause a flicker that bugged me. This uses a window command which doesn't need the delay that causes a flicker and doesn't break undo
fixes #26
Added some installation instructions for Windows users.
Fixed a markdown error
Add the line break back that was removed in #29
Merge upstream changes