Change names of test classes so nose finds them

Author: Birgit Schachler

windpowerlib/tests/density_tests.py

@@ -3,7 +3,7 @@
                                   rho_barometric, rho_ideal_gas)
 
 
-class DensityTemperatureTests:
+class TestDensityTemperature:
 
     @classmethod
     def setUpClass(self):

windpowerlib/tests/modelchain_tests.py

@@ -3,7 +3,7 @@
 from nose.tools import eq_
 
 
-class ModelchainTests:
+class TestModelchain:
 
     @classmethod
     def setUpClass(self):

windpowerlib/tests/power_output_tests.py

@@ -4,7 +4,7 @@
 import pandas as pd
 
 
-class PowerOutputTests:
+class TestPowerOutput:
 
     @classmethod
     def setUpClass(self):

windpowerlib/tests/wind_speed_tests.py

@@ -3,7 +3,7 @@
 import pandas as pd
 
 
-class WindSpeedTests:
+class TestWindSpeed:
 
     @classmethod
     def setUpClass(self):