[feature]Qiu: add grunt-seed in

grunt-seed could be used in import prepared data
[fix]Qiu: fix require('./database.js') issue

grunt-seeds and grunt-clean file loaded before setting up the process.env.NODE_ENV
and cache the object of `require('./database.js')` so that the app always use
development environment to do the database operations.

lazy load the `database.js` module in these two files
[feature]Qiu: use 'development', 'test', 'production' terms in expressjs

setup env:test before mocha test and karma test
Merge pull request #21 from twers/db-seed-and-clean

Db seed and clean