disable grading saving button after submit to prevent duplicate requests
refine achievement tests code
add a test case for destroy action
Merge pull request #273 from wangqiang1208/test/hackathon-tests

re-write announcement test cases( refine coding style )
Merge pull request #274 from wangqiang1208/bugfixing/gradings-saving-double-clicking-duplicate-requests

disable grading saving button after click submit to prevent duplicate requests
basic achievement tests (create achievements)
add delete tests for achievements. (edit tests do not work cause of absence of javascript)