Ticket #2: Create initial DB layout

Add tables for Group, Location, and Member. Members have a one-to-many
relation ship with Location, and a many-to-many relationship with Group.
In this way a member can have a single address, and belong to many
groups. Groups can simulataneously have many members, and locations can
be queried for the number of members.
Merge pull request #5 from laureltech/initialDatabase

Ticket #2: Create initial DB layout