Add unit test to prevent regression

The original autobinding diff made some assumptions about how methods were called on components that had to be reverted. This diff
enforces those assumptions in a test

src/core/__tests__/ReactCompositeComponent-test.js

@@ -188,6 +188,14 @@ describe('ReactCompositeComponent', function() {
     });
     var instance = <ComponentClass />;
 
+    // These are controversial assertions for now, they just exist
+    // because existing code depends on these assumptions.
+    expect(function() {
+      instance.methodToBeExplicitlyBound.bind(instance)();
+    }).not.toThrow();
+    expect(function() {
+      instance.methodAutoBound();
+    }).not.toThrow();
     expect(function() {
       instance.methodExplicitlyNotBound();
     }).not.toThrow();