Disable envAsHeader by default (#435)

* disable envAsHeader by default

* fix -e flag usage description

fn/routes.go

@@ -237,7 +237,9 @@ func callfn(u string, content io.Reader, output io.Writer, env []string) error {
 
 	req.Header.Set("Content-Type", "application/json")
 
+	if len(env) > 0 {
 		envAsHeader(req, env)
+	}
 
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {

fn/run.go

@@ -29,7 +29,7 @@ func runflags() []cli.Flag {
 	return []cli.Flag{
 		cli.StringSliceFlag{
 			Name:  "e",
-			Usage: "limit the environment variables sent to function, if ommited then all are sent.",
+			Usage: "select environment variables to be sent to function",
 		},
 	}
 }