Add possibility to use cacheutils's decorator on class methods

[grundic]

Hi, great module first of all!
Right now I have to use cachetools module, which provides cachedmethod decorator for using with class/instance methods.

Would it be possible to implement same for cached decorator so it would be possible to run something like:

class Example(object):
    def __init__(self):
        self._cache = LRU()

    @cached(operator.attrgetter('_cache'))
    def heavy_func(self):
        print('Called')
        return 100500

instance = Example()
for _ in range(20):
    instance.heavy_func()  # should print `Called` just once

Ideally I would prefer single decorator for generic functions and for class methods, but if it's not possible it could be implemented with two different ones.

[mahmoud]

Thank you, and yes, totally! Let me review your pull request over on #69.

[mahmoud]

This now exists, in the form of cachedmethod. Let me know how it works for you, @grundic!

[grundic]

@mahmoud, looks just awesome! Much cleaner interface and easy to use. Thank you very much!
Could you please tell when do you plane to release it on PyPI?

[mahmoud]

Glad you approve! I plan on releasing as soon as #75 is merged, so hopefully this week :)