Support LOAD_METHOD and CALL_METHOD from Python 3.7+

Fixes #163

tests/input/load_method.py

@@ -0,0 +1,15 @@
+class C:
+    def test1(self):
+        a = 1
+
+    def test2(self, x, y, z):
+        a = x * y + z
+
+    # @staticmethod -- TODO: Fix decorators
+    def testS():
+        a = 3
+
+c = C()
+c.test1()
+c.test2(42, 5, -1)
+C.testS()

tests/tokenized/load_method.txt

@@ -0,0 +1,19 @@
+class C : <EOL>
+<INDENT>
+def test1 ( self ) : <EOL>
+<INDENT>
+a = 1 <EOL>
+<OUTDENT>
+def test2 ( self , x , y , z ) : <EOL>
+<INDENT>
+a = x * y + z <EOL>
+<OUTDENT>
+def testS ( ) : <EOL>
+<INDENT>
+a = 3 <EOL>
+<OUTDENT>
+<OUTDENT>
+c = C ( ) <EOL>
+c . test1 ( ) <EOL>
+c . test2 ( 42 , 5 , - 1 ) <EOL>
+C . testS ( ) <EOL>