Removed unneeded import
Made numeric columns sort by descending first

When sorting the datatable on the main aggregation page, you probably
care most about the items with the higher total/average/max/min times.
So now, the columns sort by descending the first time you click them,
instead of ascending.
Adding Alembic stuff

See README.md for details
Merge pull request #84 from dannybutler/master

Adding Alembic stuff