renamed modules and generators to fit pep8

mathgenerator/funcs/subtraction.py

@@ -0,0 +1,14 @@
+from .__init__ import *
+
+
+def subtractionFunc(maxMinuend=99, maxDiff=99):
+    a = random.randint(0, maxMinuend)
+    b = random.randint(max(0, (a - maxDiff)), a)
+    c = a - b
+
+    problem = str(a) + "-" + str(b) + "="
+    solution = str(c)
+    return problem, solution
+
+
+subtraction = Generator("Subtraction", 1, "a-b=", "c", subtractionFunc)