hts221: add missing self parameter in getAv method.

Closes #12

Author: nedseb

lib/hts221/hts221/device.py

@@ -78,7 +78,7 @@ def setODR(self, odr=0):
         self.setReg(t | odr, HTS221_CTRL_REG1)
 
     # get/set Humidity and temperature average configuration
-    def getAv():
+    def getAv(self):
         return self.getReg(HTS221_AV_CONF)
 
     def setAv(self, av=0):