Provide a way to manually delete a cached value

[minispeck]

would be nice if there was a .del method to delete a cached value by providing a key.

myCache.del(key);

love the simplicity of this library - but imo it needs a delete method.

currently we are using a workaround:

myCache.set(key, '', {'expire': 1});

not the most elegant. i would have expected that setting null or undefined would be equivalent to deleting but that doesnt seem to be the case.

[jkrems]

Thanks to @fdegiuli there's a myCache.unset(key) starting with cached@4.3.0. In case you still need it. :)