update readme to include release documentation

README.md

@@ -20,3 +20,22 @@ To pull in recent changes from the upstream repo run the following:
 ```console
 git subtree pull -P depend/zcash <repo> <branch> --squash
 ```
+
+For example:
+
+```console
+git subtree pull -P depend/zcash https://github.com/str4d/zcash.git zcash-script-precompute --squash
+```
+
+### Publishing New Releases
+
+Releases for `zcash-script` are made with the help of [cargo release](https://github.com/sunng87/cargo-release).
+
+**Checklist:**
+
+* create a new branch batch the release commits into a PR
+* update `CHANGELOG.md` to document any major changes since the last release
+* open a PR to merge your branch into `master`
+* locally run `cargo release -- <level>` where `level` can be `patch`, `minor`, or `major` ([source](https://github.com/sunng87/cargo-release/blob/master/docs/reference.md#bump-level))
+
+**NOTE**: It's important to specify the level when using cargo release because of the way it implements the substitutions. We specify a number of automatic substitutions in `Cargo.toml` but they will only be applied if `cargo release` also handles incrementing the version itself, **do not increment the version by hand and then run `cargo release` or `cargo release -- release`, or it will not correctly update all version references in the codebase.**