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/konsorten/go-windows-terminal-sequences/README.md

@@ -0,0 +1,41 @@
+# Windows Terminal Sequences
+
+This library allow for enabling Windows terminal color support for Go.
+
+See [Console Virtual Terminal Sequences](https://docs.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences) for details.
+
+## Usage
+
+```go
+import (
+	"syscall"
+	
+	sequences "github.com/konsorten/go-windows-terminal-sequences"
+)
+
+func main() {
+	sequences.EnableVirtualTerminalProcessing(syscall.Stdout, true)
+}
+
+```
+
+## Authors
+
+The tool is sponsored by the [marvin + konsorten GmbH](http://www.konsorten.de).
+
+We thank all the authors who provided code to this library:
+
+* Felix Kollmann
+* Nicolas Perraut
+
+## License
+
+(The MIT License)
+
+Copyright (c) 2018 marvin + konsorten GmbH (open-source@konsorten.de)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

vendor/github.com/konsorten/go-windows-terminal-sequences/go.mod

@@ -0,0 +1 @@
+module github.com/konsorten/go-windows-terminal-sequences