chore: update doc

Author: liuqiangqiang

README.md

@@ -1,7 +1,9 @@
 # Flow
 🌊Flow is an easy-used concurrent calculate model in Go.
+
 Flow can easily limit the maxium number of concurrent goroutine and can be very straight-forward to use.
-Basically, flow is a 2d matrix and it runs jobs row-by-row and all the jobs in same row will run concurrently.
+
+Basically, flow is a 2D matrix and it run jobs row-by-row which in same row, the jobs will run concurrently.
 
 # Example
 ```Go
@@ -20,10 +22,7 @@ func main() {
 		counter++
 		fmt.Println("level", counter)
 	}
-	// Next start a new level, and put the job `showLevel` in this level
-	// the first level will be created by Flow
-	// so you can also use With to add showLevel in the first level
-	// f.With(showLevel)
+	// Next starts a new level, and put the job `showLevel` in it
 	f.Next(showLevel)
 	for i := 0; i < 20; i++ {
 		v := i

flow_test.go

@@ -14,10 +14,7 @@ func Example() {
 		counter++
 		fmt.Println("level", counter)
 	}
-	// Next start a new level, and put the func `showLevel` in this level
-	// the first level will be created by Flow
-	// so you can also use With to add showLevel in the first level
-	// f.With(showLevel)
+	// Next starts a new level, and put the job `showLevel` in it
 	f.Next(showLevel)
 	for i := 0; i < 20; i++ {
 		v := i