Support users who prefer to manually enable Evil on a per-buffer basis

[fritzgrabo]

Support users who prefer to manually enable evil-local-mode on a per-buffer basis (vs. enabling Evil in all buffers via the global evil-mode). This should be a safe change because the global evil-mode automatically enables the buffer-local one in all covered buffers, too.

Update stale Makefile and tests.

Thanks for this awesome package 🙇 🎉