all: Become a Go module (fixes #5148) (#5384)

* go mod init; rm -rf vendor

* tweak proto files and generation

* go mod vendor

* clean up build.go

* protobuf literals in tests

* downgrade gogo/protobuf

vendor/github.com/gobwas/glob/.travis.yml

@@ -0,0 +1,9 @@
+sudo: false
+
+language: go
+
+go:
+  - 1.5.3
+
+script:
+  - go test -v ./...