Transitive dependency on github.com/dgrijalva/jwt-go

[Colin Douch]

Hi!

Through the dependency on go-kit/k...@v0.11.0, jaegertracing/jaeger depends on github.com/dgrijalva/jwt-go. There are a slew of vulns against that repo (e.g. https://github.com/dgrijalva/jwt-go/issues/428) and it is abandoned in favour of https://github.com/golang-jwt/jwt . go-kit 0.12.0 upgrades to the new repo, so can we update jaegertracing/jaeger to go-kit 0.12.0 to mitigate this?

- Colin