Update to last common bleve (#3986)

vendor/github.com/couchbase/vellum/CONTRIBUTING.md

@@ -0,0 +1,16 @@
+# Contributing to Vellum
+
+We look forward to your contributions, but ask that you first review these guidelines.
+
+### Sign the CLA
+
+As Vellum is a Couchbase project we require contributors accept the [Couchbase Contributor License Agreement](http://review.couchbase.org/static/individual_agreement.html). To sign this agreement log into the Couchbase [code review tool](http://review.couchbase.org/). The Vellum project does not use this code review tool but it is still used to track acceptance of the contributor license agreements.
+
+### Submitting a Pull Request
+
+All types of contributions are welcome, but please keep the following in mind:
+
+- If you're planning a large change, you should really discuss it in a github issue first. This helps avoid duplicate effort and spending time on something that may not be merged.
+- Existing tests should continue to pass, new tests for the contribution are nice to have.
+- All code should have gone through `go fmt`
+- All code should pass `go vet`