Revert "switching db gem for use in heroku."

This reverts commit 55aefb34c6aa306d0c6bf117aff0089b8a6c650f.
changing the ids for the svg district elements in start.html.erb. This is a fix for a bug where the incoming data had a leading '0' for the district numbers in some cases. The solution is to just add that leading zero into our map ids