New download paths

Since mesos 0.19.0 the download url for the deb and rpm packages has changed. This PR changes it accordingly and bumps the default mesos version to the current 0.20.1.
By switching to this logic for finding mesos packages we would be unable to run any packages that do not conform to this filename creation logic.  For instance this will break for version 0.18.2 and older so this cookbook would need to make clear that it's intended to support version 0.19.0+