Resolve "Implement basic structure for the hexagon experiment"

Closes #94 (closed)

• New Hexagon class for hexagon simulations
• A few associated unit tests

lisainstrument/hexagon.py

@@ -151,7 +151,7 @@ class Hexagon():
 
             hdf5.attrs['primary_laser_asd'] = self.primary_laser_asd
             hdf5.attrs['locked_laser_asd'] = self.locked_laser_asd
-            hdf5.attrs['offset_freqs'] = self.offset_freqs
+            hdf5.attrs['offset_freqs'] = str(self.offset_freqs)
             hdf5.attrs['central_freq'] = self.central_freq
 
             logger.debug("Saving simulated data")