Move tests in basic/tests/ up one level preparating to multiple test dirs.

tests/basics/class_number.py

@@ -0,0 +1,15 @@
+# test class with __add__ and __sub__ methods
+
+class C:
+    def __init__(self, value):
+        self.value = value
+
+    def __add__(self, rhs):
+        print(self.value, '+', rhs)
+
+    def __sub__(self, rhs):
+        print(self.value, '-', rhs)
+
+c = C(0)
+c + 1
+c - 2