Added a feature that allows you to increment integers

This is a feature that I thought was needed for something like this. It allows you to increment values if they are integers. EG:

`curl --data "column=1&label=Cups%20Of%20Tea%20Made&value=1" http://localhost:9999`

Displays 'Cups Of Tea Made: 1' on the dash.

`curl --data "column=1&label=Cups%20Of%20Tea%20Made&value=4&increment=true" http://localhost:9999`

Displays `Cups Of Tea Made: 5' on the dash.