Caching for requests that doesn't have the last-modified header about bnet

[jyggen]

I thought about this back when I implemented support for the If-Modified-Since and Last-Modified headers and the conclusion back then was to not cache requests without headers at all since I didn't really want the library to make assumptions/behave unexpectedly.

The data from the classes/races endpoints should preferably be stored in a database and only be updated once per expansion, but if people want to waste they rate limits on that data then I think we should let them. If Blizzard wanted us to cache these requests they would've added a Last-Modified header to the responses :)

[morloderex]

True, but neverless i think we should allow for setting a custom cache time just for the optionalism it creates.

[jyggen]

Closing this since it's now out-of-scope for this library.