Module#method_added

Specs fixed:

Module#method_added
- returns nil in the default implementation
- is called when a new method is defined in self
BasicObject#singleton_method_added

Specs fixed:

BasicObject#singleton_method_added
- is called when a method is defined on self
- is called when a method is defined in the singleton class
- is called when define_method is used in the singleton class
Module#method_undefined

Specs fixed:

Module#method_undefined
- returns nil in the default implementation
- is called when a method is undefined from self
BasicObject#singleton_method_undefined

Specs fixed:

BasicObject#singleton_method_undefined
- is called when a method is removed on self
Tagged failing specs

This specs will be failing untill method visibility is implemented.
Do not forget to copy attached instance too
Merge pull request #674 from krekoten/module_method_hooks

Module method_* hooks