Merge branch 'an/prometheus' into 'master'

vendor/github.com/golang/protobuf/LICENSE

vendor/github.com/golang/protobuf/proto/Makefile

vendor/github.com/golang/protobuf/proto/clone.go

vendor/github.com/golang/protobuf/proto/decode.go

vendor/github.com/golang/protobuf/proto/discard.go

vendor/github.com/golang/protobuf/proto/encode.go

vendor/github.com/golang/protobuf/proto/equal.go

vendor/github.com/golang/protobuf/proto/extensions.go

vendor/github.com/golang/protobuf/proto/lib.go

vendor/github.com/golang/protobuf/proto/message_set.go

vendor/github.com/golang/protobuf/proto/pointer_reflect.go

vendor/github.com/golang/protobuf/proto/pointer_unsafe.go

vendor/github.com/golang/protobuf/proto/properties.go

vendor/github.com/golang/protobuf/proto/table_marshal.go

vendor/github.com/golang/protobuf/proto/table_merge.go

vendor/github.com/golang/protobuf/proto/table_unmarshal.go

vendor/github.com/golang/protobuf/proto/text.go

vendor/github.com/golang/protobuf/proto/text_parser.go

...thub.com/prometheus/client_golang/prometheus/collector.go

...github.com/prometheus/client_golang/prometheus/counter.go