Cleaned up python tutorials and added dependency checks to all tutorials

Former-commit-id: 246017f041

python/tutorial/509_Planarization.py

@@ -1,6 +1,4 @@
 import sys, os
-import random
-from math import cos, sin, pi
 
 # Add the igl library to the modules search path
 sys.path.insert(0, os.getcwd() + "/../")
@@ -12,7 +10,6 @@ dependencies = ["viewer"]
 check_dependencies(dependencies)
 
 
-
 viewer = igl.viewer.Viewer()
 
 # Quad mesh generated from conjugate field