replace github.com/golang/protobuf with google protobuf

[ahrycej]

Replace the github.com/golang/protobuf-1.5.3 with google code

The whole project seem to be depricated and it is recommended to go for google
from
https://github.com/golang/protobuf

"It has been superseded by the google.golang.org/protobuf module, which contains an updated and simplified API, support for protobuf reflection, and many other improvements. We recommend that new code use the google.golang.org/protobuf module.

Versions v1.4 and later of github.com/golang/protobuf are implemented in terms of google.golang.org/protobuf. Programs which use both modules must use at least version v1.4 of this one."

[edoger]

To solve this problem, you need to start from github.com/prometheus/common, the ultimate reason is that github.com/prometheus/common depends on github.com/matttproud/golang_protobuf_extensions (very old and out of date).

[rufreakde]

Linking issue: prometheus/common#317

[pavelpatrin]

+1