Switch to go mod

vendor/github.com/vbatts/go-mtree/releases.md

@@ -0,0 +1,11 @@
+# How to do releases:
+
+* Create a changeset with an update to `version.go`
+ - this commit will be tagged
+ - add another commit putting it back with '-dev' appended
+* gpg sign the commit with an incremented version, like 'vX.Y.Z'
+* Push the tag
+* Create a "release" from the tag on github
+ - include the binaries from `make build.arches`
+ - write about notable changes, and their contributors
+ - PRs merged for the release