README.md in embulk-input-randomj-0.4.0 vs README.md in embulk-input-randomj-0.5.0

@@ -12,11 +12,11 @@
 * **Plugin type**: input
 * **Resume supported**: no
 * **Cleanup supported**: no
 * **Guess supported**: no
 
-## Install 
+## Install
 
 ``` shell
 % embulk gem install embulk-input-randomj
 ```
 
@@ -57,10 +57,29 @@
       - {name: named,    type: string, length: 12}
       - {name: price,    type: long, max_value: 1080, min_value: 100}
       - {name: purchase, type: timestamp, format: '%Y/%m/%d'}
 ```
 
+Add `null_rate` option (from 0.4.0)
+
+This configuration is that inserted `null` into `price` filed with a probability `8` of 10000.
+
+```yaml
+in:
+    type: randomj
+    rows: 16
+    threads: 1
+    primary_key: myid
+    schema:
+      - {name: myid,     type: long}
+      - {name: named,    type: string, length: 12}
+      - {name: price,    type: long, max_value: 1080, min_value: 100, null_rate: 8}
+      - {name: purchase, type: timestamp, format: '%Y/%m/%d'}
+```
+
+
+
 ## Usage
 
 ### Example1
 
 ```shell
@@ -78,11 +97,11 @@
       - {name: x_flag,   type: boolean}
       - {name: pit_rate, type: double}
       - {name: score,    type: long}
       - {name: time,     type: timestamp, format: '%Y-%m-%d %H:%M:%S'}
       - {name: purchase, type: timestamp, format: '%Y/%m/%d'}
-  
+
   out:
     type: stdout
 
 
 % embulk run -I lib example/config.yml
@@ -114,11 +133,11 @@
 
 ### Example2
 
 - `named_s` return string with length 8
 - `score` return value between `100~255`
-- `rate` return value between `-100~100` 
+- `rate` return value between `-100~100`
 
 ```shell
 
 % cat example/config.yml
 in:
@@ -174,10 +193,10 @@
 ```
 $ ./gradlew gem  # -t to watch change of files and rebuild continuously
 ```
 
 ```
-$ ./gradlew build && ./gradlew classpath 
+$ ./gradlew build && ./gradlew classpath
 $ embulk run -I lib config/example.yml     
 ```
 
 
 ## ChangeLog