Add support for installing Statsd Proxy

* New recipe: statsd::proxy which installs the Statsd Proxy service
* Using chefspec to test the cookbooks, added support for Berkshelf
Add support for specifying chef role

* Chef role added as configurable attribute
* Added extra defaults for cache_size and check_interval
Merge pull request #2 from daanemanz/add-statsd-proxy-support

Add support for installing Statsd Proxy