use new RunAndGet in README.md because it is more simpler

Author: rainu

README.md

@@ -15,24 +15,24 @@ cat log_file.txt | grep error | wc -l
 package main
 
 import (
-	"bytes"
 	"fmt"
 	"github.com/rainu/go-command-chain"
 )
 
 func main() {
-	output := &bytes.Buffer{}
-
-	err := cmdchain.Builder().
+	stdOut, stdErr, err := cmdchain.Builder().
 		Join("cat", "log_file.txt").
 		Join("grep", "error").
 		Join("wc", "-l").
-		Finalize().WithOutput(output).Run()
+		Finalize().RunAndGet()
 
 	if err != nil {
 		panic(err)
 	}
-	fmt.Printf("Errors found: %s", output)
+	if stdErr != "" {
+		panic(stdErr)
+	}
+	fmt.Printf("Errors found: %s", stdOut)
 }
 ```
 

example_test.go

@@ -237,3 +237,19 @@ func ExampleBuilder_run() {
 	}
 	println(output.String())
 }
+
+func ExampleBuilder_runAndGet() {
+	//it's the same as in shell: ls -l | grep README | wc -l
+	sout, serr, err := cmdchain.Builder().
+		Join("ls", "-l").
+		Join("grep", "README").
+		Join("wc", "-l").
+		Finalize().
+		RunAndGet()
+
+	if err != nil {
+		panic(err)
+	}
+	println("OUTPUT: " + sout)
+	println("ERROR: " + serr)
+}