Implemented a linked list in FrontLinkedList.py to be used by a LRU cache that will be implemented; added a null-object cache and plugged in as default caching strategy; provided base abstraction for OWM caches (the OWMCache abstract class) [ci skip]
Implemented an LRU (Least Recently Used) cache provider; modified OWM 2.5 configuration so that embeds a cache provider - defaulted to a null-object cache; provided a new functional test; modified docs
Fixed import error
Release 0.4.0: implemented a basic cache system for the PyOWM library. Fixed import about timeutils.py module which was broken