Remove travis config

.travis.yml

@@ -1,32 +0,0 @@
-go_import_path: github.com/spf13/viper
-
-language: go
-
-env:
-  global:
-    - GO111MODULE="on"
-    - GOFLAGS="-mod=readonly"
-
-go:
-  - 1.11.x
-  - 1.12.x
-  - 1.13.x
-  - tip
-
-os:
-  - linux
-  - osx
-
-matrix:
-  allow_failures:
-    - go: tip
-  fast_finish: true
-
-script:
-  - go install ./...
-  - diff -u <(echo -n) <(gofmt -d .)
-  - go test -v ./...
-
-after_success:
-  - go get -u -d github.com/spf13/hugo
-  - cd $GOPATH/src/github.com/spf13/hugo && make && ./hugo -s docs && cd -