fix(cli): Add entry point for CLI

It seems we forgot to add an entry point where we originally created the CLI.  This should fix it.

I also realized that the command doesn't give any indication of the simulation progress so I am adding a print statement so that people aren't left hanging for over a minute without any indication of how much longer the simulation will take.

We should ass an option to silence this reporting for those who don't want it.

CC: @saeranv

uwg/__main__.py

@@ -0,0 +1,4 @@
+from uwg.cli import main
+
+if __name__ == '__main__':
+    main()

uwg/uwg.py

@@ -1207,7 +1207,10 @@ def simulate(self):
               '{} days from {}/{}.'.format(self.nday, self.month, self.day))
 
         # iterate through every simulation time-step (i.e 5 min) defined by UWG
+        day_step = int((1 / self.ph) * 24)
         for it in range(1, self.simTime.nt, 1):
+            if it % day_step == 0:
+                print('Simulating Day {}'.format(int(it / day_step)))
             # Update water temperature (estimated)
             if self.nSoil < 3:
                 # for BUBBLE/CAPITOUL/Singapore only