Upgrade `mvcc` to `2.0.0-alpha.2`.
Upgrade `mvcc` to `2.0.0-alpha.2`.

MVCC 2.0.0-alpha.2 had some `package.json` tidy.

https://github.com/bigeasy/mvcc/releases/tag/v2.0.0-alpha.2

Closes #89.

bigeasy/advance,bigeasy/advance