db tasks - clear down & seed

Added two grunt tasks that will allow you to do a clear down of the database and also seed it. Make sure you have the grunt-cli installed globally (```npm install -g grunt-cli```)

To clear down run ```grunt db-clear```
To seed run ```grunt db-seed``` (note: this will run db-clear first)

Currently the seed does the minimum and just adds a dummy user and news item (with initial vote). This method has far too much nesting and needs to be broken up a little, and over time we can add to it as we need.