Investigate concurrency issues

[geoffxy]

• [x] Add logging to node process to get visibility into errors
• [x] Shorten length of patches that are pure insertions and pure deletions (to allow concurrent edits near the same region)
• [x] Investigate why sometimes the index to point mapping exceeds the bounds of the buffer
• [x] Build some kind of fuzzer to facilitate testing concurrent edits
• [x] Use sync calls in neovim instead of async_call

[geoffxy]

FYI - We don't really need the fuzzer anymore since I found out you can have simultaneous input to two panes using iTerm.

[geoffxy]

Hopefully this has been fixed now.