Update Tekton api client to 0.15 (#262)

* update tekton api client to 0.15

* update doc versioning

* Update tekton_kfp_guide.md

go.mod

@@ -16,8 +16,7 @@ require (
 	github.com/go-openapi/validate v0.19.5
 	github.com/go-sql-driver/mysql v1.5.0
 	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
-	github.com/golang/protobuf v1.4.0
-	github.com/google/addlicense v0.0.0-20200622132530-df58acafd6d5 // indirect
+	github.com/golang/protobuf v1.4.2
 	github.com/google/go-cmp v0.4.1
 	github.com/google/uuid v1.1.1
 	github.com/gopherjs/gopherjs v0.0.0-20181103185306-d547d1d9531e // indirect
@@ -28,17 +27,16 @@ require (
 	github.com/peterhellberg/duration v0.0.0-20191119133758-ec6baeebcd10
 	github.com/pkg/errors v0.9.1
 	github.com/robfig/cron v1.2.0
-	github.com/sirupsen/logrus v1.4.2
-	github.com/spf13/viper v1.6.2
+	github.com/sirupsen/logrus v1.6.0
+	github.com/spf13/viper v1.7.0
 	github.com/stretchr/testify v1.5.1
-	github.com/tektoncd/pipeline v0.14.0
+	github.com/tektoncd/pipeline v0.15.0
 	github.com/valyala/fasttemplate v1.1.0 // indirect
-	golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e
+	golang.org/x/net v0.0.0-20200520182314-0ba52f642ac2
 	golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208 // indirect
-	google.golang.org/api v0.20.0
-	google.golang.org/genproto v0.0.0-20200326112834-f447254575fd
-	google.golang.org/grpc v1.28.0
-	gopkg.in/ini.v1 v1.56.0 // indirect
+	google.golang.org/api v0.25.0
+	google.golang.org/genproto v0.0.0-20200527145253-8367513e4ece
+	google.golang.org/grpc v1.29.1
 	gopkg.in/yaml.v2 v2.3.0
 	k8s.io/api v0.17.6
 	k8s.io/apimachinery v0.17.6