[Update by Gordon Tsai at Aug 27]
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[Newly Done]
1. [Done-10]

[Done]
1. (tempalately)Use user.json to specified user identity.
2. Server open the material folder depends on user.For example, AOOP's permanent ID is UEE1303，and I took this class in 102B(current ID:1060)，so when I
   view the AOOP material，what I see would be UEE1303/1060.
3. Be able to get file names in dir,but failed to load it to the page.
4. Improved user.json format.
5. Fixed:Failed to get JSON file property .(\handlers\materials.js :Line 92)
6. Fixed:function load_material should be rewrite with async.waterfall or something else,rather than nested structure.(\handlers\materials.js :Line80-148)
7. Fixed:Failed to read files from dir.
8. Fixed:Failed to load file to the page,but it absolutely has got files' name.(\material\content\material.js :Line33)
9. Fixed:Disign the page of showing up material files.(It is currently the form of the example in the textbook.)
10.Fixed:The browser failed to get material file from server.

[Wait for improved]
1.Clean up all of the test code such as "console.log",etc.
2.Some useful functions in load_material (\handlers\materials.js) should be separated ,and rewrited into named functions.

[Wait for discussion]
1. Improve the format of user json.
2. (\handlers\material_helper.js Line24)