Prefer ChaCha20 for speedy SSH cipher

- `blowfish-cbc` is unavailable in newer OpenSSH on Arch
- still use it as a fallback, as ChaCha20 is only available in newer
- ChaCha20 = DJB
Allow specifying current SYNERGY host via `.`

E.g.: `SYNERGY a . b` means:

┌─┬─────────┬─┐
│a│localhost│b│
└─┴─────────┴─┘

Technically, so does `SYNERGY b a`:

┌─┬─┬─────────┐
│b│a│localhost│
└─┴─┴─────────┘

But, usually `a . b` is a more reasonable first pass at entering it.
Change `build-vim` to not start instance

- was written when testing something re: window borders
- makes more sense to just print the newly installed version