upgrade prometheus client-go

Signed-off-by: zackzhangkai <zackzhang@yunify.com>

vendor/github.com/opentracing/opentracing-go/.travis.yml

@@ -1,20 +0,0 @@
-language: go
-
-matrix:
-  include:
-  - go: "1.11.x"
-  - go: "1.12.x"
-  - go: "tip"
-    env:
-    - LINT=true
-    - COVERAGE=true
-
-install:
-  - if [ "$LINT" == true ]; then go get -u golang.org/x/lint/golint/... ; else echo 'skipping lint'; fi
-  - go get -u github.com/stretchr/testify/...
-
-script:
-  - make test
-  - go build ./...
-  - if [ "$LINT" == true ]; then make lint ; else echo 'skipping lint'; fi
-  - if [ "$COVERAGE" == true ]; then make cover && bash <(curl -s https://codecov.io/bash) ; else echo 'skipping coverage'; fi