Promotion Item Total Rule to include Upper limit also

Add 'less than' and 'less than or equal to' to ItemTotal Rule in promotions.

This is required in the following scenario:

There are multiple promotions from which only one is applicable at a time based on the cart amount(Item Total).

Small Cart Promotion : 5% discount if ItemTotal is between 100 and 200 
Medium Cart Promotion : 10% discount if ItemTotal is  between 200 and 400
Large Cart Promotion : 15% discount if ItemTotal is  greater than 400

![item_total](https://f.cloud.github.com/assets/1397023/2501863/d3b0046e-b370-11e3-9c53-a8d0abdd7f46.png)