doc: update readme.

Author: ghosind

README.md

@@ -22,12 +22,17 @@ This library provided assertion functions to verify the equality of values, or a
 
 ```go
 func TestExample(t *testing.T) {
+  // var actual
+  // var expect
+
   // assert equality
   assert.DeepEqual(t, actual, expect)
 
   // assert inequality
   assert.NotDeepEqual(t, actual, expect)
 
+  // var object
+
   // assert for nil
   assert.Nil(t, object)
 
@@ -56,6 +61,21 @@ func TestPanic(t *testing.T) {
 }
 ```
 
+For every assertion functions, it also provided `XXXNow` functions to stop the execution.
+
+```go
+func TestExample(t *testing.T) {
+  // var actual
+  // var expect
+
+  // The following line will set the test result to fail and stop the execution
+  assert.DeepEqualNow(t, actual, expect)
+
+  // The following lines will never execute if they are not deep equal.
+  // ...
+}
+```
+
 Every assertion will not terminate the testing workflow. However, they'll return an error if the verification failed, and you can check the return value to get the verification result.
 
 ```go