Dropped play_count support

According to pullrequest #40 (bugs with repeated access to same page in once mode), I prepared simple (not yet valid) patch.

The problem is 
* Imagine that http://httpbin.org/random/ servers page with random number (or time). Should the repeated requests via vcrpy to this page get still same number, or different one? This patch will serve still the same number, which I don't feel to be right.

Feel free to accept or reject this patch.