Don't push untested changes to master

[ksamuel]

I made a PR for the a typo in the last commit that was crashing the sentinel. See: #6

However, the official tutorial to install the sentinel for the masternode uses the master branch, so if you break it, you break all new installs and update.

Create a dev branch, and work on this separately until you are sure the sentinel is working properly, at which moment you can merge it into master.