fix(scripts): change supervisor command format
The start script used to run supervisor with 'supervisor -w ./lib/server.js ./lib/server.js'. This caused issues when trying to call DeltaBot with command line arguments. supervisor would interpret the arguments as arguments for itself instead of arguments for the node package. As a result, DeltaBot would not run when called with arguments and would simply print supervisor's help message.
By changing the start script to 'supervisor -w ./lib/server.js -- ./lib/server.js' supervisor correctly interprets arguments passed to 'npm start' as arguments for the node package.