Add travisCI config
Add travisCI config

Summary: Add a travisCI config for flog. Testing latest versions of go 1.10, 1.11, 1.12 and 1.13.

Reviewed By: yarikk

Differential Revision: D17664208

fbshipit-source-id: dcd488bc73ce2be80704646dd7604cca291139a1

facebookincubator/flog