Cache decorators should never raise exceptions

Since decorators are used for caching purposes, it is reasonable to assume that they are used only for speedups. So I think cache decorators should never raise exceptions. 

Developers want speedups, but usually assume that they code will never break because of them.

Also, I've added Sam Zaydel [1] name in setup.py, which will list his name on PyPI if this pull request is accepted and I update the PyPI package to this 0.0.4 version.

[1] Sam contributed with this Pull Request: https://github.com/vivekn/redis-simple-cache/pull/5