Update to use go modules (#671)

This includes updates to CI config, vendor files, etc.
I've hard-coded the k8s depedency at 1.13.4 to keep it inline with what
we currently have and to make sure a another run of `go mod tidy`
doesn't accidentally update it to an unexpected version.

Thanks to hectorj2f for carrying this along.

vendor/github.com/json-iterator/go/iter_skip_strict.go

@@ -2,12 +2,22 @@
 
 package jsoniter
 
-import "fmt"
+import (
+	"fmt"
+	"io"
+)
 
 func (iter *Iterator) skipNumber() {
 	if !iter.trySkipNumber() {
 		iter.unreadByte()
-		iter.ReadFloat32()
+		if iter.Error != nil && iter.Error != io.EOF {
+			return
+		}
+		iter.ReadFloat64()
+		if iter.Error != nil && iter.Error != io.EOF {
+			iter.Error = nil
+			iter.ReadBigFloat()
+		}
 	}
 }