Client should validate the incoming host value

Convert host:port and URLs passed to client.New() into the proper
values, and return an error if the value is invalid.  Change CLI
to return an error if -master is invalid.  Remove Client.rawRequest
which was not in use, and fix the involved tests. Add NewOrDie

Preserves the behavior of the client to not auth when a non-https
URL is passed (although in the future this should be corrected).

pkg/client/request.go

@@ -56,7 +56,7 @@ func (c *RESTClient) Verb(verb string) *Request {
 	return &Request{
 		verb:       verb,
 		c:          c,
-		path:       c.Prefix,
+		path:       c.prefix,
 		sync:       c.Sync,
 		timeout:    c.Timeout,
 		params:     map[string]string{},