Contains common code for Xton's vim emulation (vimulation?) layer.
Inspired/stolen from the ergodox_ez/vim keymap. Rewritten to be a more straightforward state machine and support more macros. Vim layers _CMD and _EDIT are designed to lay on top of an otherwise fully-functional layout. _CMD runs the entire vim state machine while _EDIT should lay across your base layer and mask off just the escape key.
Works via OSX text editing shortcuts, mainly MOD+arrow combinations. This has some limitations and only works on OSX.
The _CMD layer will temporarily disable itself while CMD or ALT are held down so that typical OSX shortcuts can be used without switching out of vim mode.