Update default package version to install to 1.8.1
Update default package version to install to 1.8.1

For some reason I was never able to get 1.7.1 to install from the source repo @ bintray -- but 1.8.1 works just fine.  Tested with 'vagrant up' from a git clone.
JustinAiken/openhab-cookbook,JustinAiken/openhab-cookbook