Added active uncompleted tasks count for a lists

Hi Ali,

I already wrote you via Twitter and here is the pull request for my changes to your Cheddar-Android app :) I send you my "develop" branch for merging. I'm using the "git flow" model and merged the feature branch for "active tasks count" already into "develop".

Some facts about my changes:
I kicked out the PullToRefresh library, because I thought the refresh via ActionBar (like you do in the TasksActivity) is better for the user experience.

There are some additions I want to make, e.g. the refresh animation when starting the app. But I/we can do it later :)

Cheers,
Marcus