Release Amalgamate version 0.1.23.
Release Amalgamate version 0.1.23.

 * Upgrade `riffle` to `2.0.0-alpha.33`. Closes #134.
 * Upgrade `b-tree` to `2.0.0-alpha.51`. Closes #133.
 * Upgrade `splice` to `3.0.0-alpha.20`. Closes #132.

Closes #135.

bigeasy/amalgamate,bigeasy/amalgamate