create AbstractFileUploadService and make PictureService extends from it.
add ZipService class and service method about upload contest ZIP archive.
move uploadFile method to utils.
Merge pull request #34 from pfctgeorge/contest-management

refactor service about file upload and add ZipService
[UPDATE] Add contest rank list

Change-Id: I13bcab59d40721b82cb1cd88374d8994d9a3310d
[UPDATE] Compile grunt project

Change-Id: Ieed59c85fa6051084978caf8e798aa5f9536495a
Merge pull request #36 from mzry1992/mzry1992

Add contest rank list.
Merge pull request #38 from lyhypacm/travis-support

Add Travis support