Add 'support' for old-style classes by converting the new-style classes for now
implement delete attribute by reorganize hidden class
modify the procedure of looking up descriptor and add some comments
Merge branch 'public' into personal
Merge branch 'delattr_by_hcls' of https://github.com/xiafan68/pyston into personal

Merges #101

Conflicts:
	src/codegen/runtime_hooks.h