Fix deploy problem with dart.
Merge pull request #16 from niczy/master

There's some thing wrong with the style.
Add text importer and some basic entities
Add some sample exams (in text and doc)
Revert "Add some sample exams (in text and doc)"

This reverts commit 2011393b244f3ad79e7e262cf716985ed9d03d8c.
Revert "Add text importer and some basic entities"

This reverts commit 2fe62dc583e7d291927f39fb75801e99ae48e21e.
Revert "Rename "server" directory to "tools""

This reverts commit 5753b806e5162ec787f7b72fee40d1a3c7ec284f.
Revert "Add encoder from json to datastore entity"

This reverts commit b421dc0f6f02b870f04bbd762798e99f6317b679.