Add HashiCorp Nomad provider (#483)

* provider: adding Nomad provider

* updating CONTRIBUTING.md with Nomad provider

* updated README.md by adding the Nomad provider

* fix typo

* adding nomad/api and nomad/testutil deps

* adding Nomad binary dependency for provider tests

* fixed the nomad binary download command step and added tolerations to the nomad provider.

* adding nomad provider demo gif

* adding my name to authors

* adding two missing go-rootcerts files after dep ensure

* delete pod comment

vendor/github.com/hashicorp/go-cleanhttp/doc.go

@@ -0,0 +1,20 @@
+// Package cleanhttp offers convenience utilities for acquiring "clean"
+// http.Transport and http.Client structs.
+//
+// Values set on http.DefaultClient and http.DefaultTransport affect all
+// callers. This can have detrimental effects, esepcially in TLS contexts,
+// where client or root certificates set to talk to multiple endpoints can end
+// up displacing each other, leading to hard-to-debug issues. This package
+// provides non-shared http.Client and http.Transport structs to ensure that
+// the configuration will not be overwritten by other parts of the application
+// or dependencies.
+//
+// The DefaultClient and DefaultTransport functions disable idle connections
+// and keepalives. Without ensuring that idle connections are closed before
+// garbage collection, short-term clients/transports can leak file descriptors,
+// eventually leading to "too many open files" errors. If you will be
+// connecting to the same hosts repeatedly from the same client, you can use
+// DefaultPooledClient to receive a client that has connection pooling
+// semantics similar to http.DefaultClient.
+//
+package cleanhttp