airfoil clean up and versioning

Author: planes

C172_Tutorial/Airfoils/NACA_4412.txt renamed to Airfoils/NACA_4412.txt

@@ -9,6 +9,7 @@
 
 # pacakgee imports
 import SUAVE
+assert SUAVE.__version__=='2.5.2', 'These tutorials only work with the SUAVE 2.5.2 release'
 import numpy as np
 
 # module imports

C172_Tutorial/Airfoils/Polars/NACA_4412_polar_Re_100000.txt renamed to Airfoils/Polars/NACA_4412_polar_Re_100000.txt

@@ -7,6 +7,7 @@
 #   Imports
 # ----------------------------------------------------------------------
 import SUAVE
+assert SUAVE.__version__=='2.5.2', 'These tutorials only work with the SUAVE 2.5.2 release'
 from SUAVE.Core import Units
 
 import pylab as plt