write the readme.md

README.md

 # Filename input plugin for Embulk
 
-TODO: Write short description here and build.gradle file.
 
 ## Overview
 
 * **Plugin type**: input
-* **Resume supported**: yes
+* **Resume supported**: not yet
 * **Cleanup supported**: yes
 * **Guess supported**: no
 
 ## Configuration
 
-- **option1**: description (integer, required)
-- **option2**: description (string, default: `"myvalue"`)
-- **option3**: description (string, default: `null`)
+- **multi_dir**: description (ArrayList<String>, required)
+- **mulit_tag**: description (ArrayList<String>, default: `[]`)
+- **order_by_modified_time**: description (int, default: `0`)
+- **order_by_creation_time**: description (int, default: `0`)
+- **chunk_size**: description (int, default: `10485760(10M)`)
 
 ## Example
 
 ```yaml
 in:
-  type: filename
-  option1: example1
-  option2: example2
+  type: filename 
+  mulit_dir: ["../sample/sample_","../example/example_"]
+  multi_tag: ["tag1","tag2"]
+  order_by_modified_time: 1
+  chunk_size: 1000
 ```
+For the order_by_modified_time option, its default value is 0, the files in each directory are uploaded in alphabetical order.
+If it equals 1, the files in each directory will be uploaded in the order of their last modified time. 
+if it equals neither 1 or 0, the files will be uploaded in descend order of their last modified time.
+The order_by_modified_time is the same like order_by_modified_time. Those two option could not be set at same time since the you have to choose 
+only one order to upload the files. And the order_by_creation_time is useless in Unix system as the unix system does not record the creation 
+time of the files. Use the order_by_creation_time sparingly.
 
 
 ## Build
+java 1.8 is required.
 
 ```
 $ ./gradlew gem  # -t to watch change of files and rebuild continuously