Caching and conditional requests

[schwern]

Github supports the awkwardly named Conditional Requests to check if a resource has been modified. This allows one to cache API responses and cheaply check if there has been a change.

I plan on adding cache support to Net::GitHub::V3, on by default, with a simple Least Recently Used cache limited by number of queries stored. I plan on adding it at the query level so every query is cached. This allows Gitpan to make API requests as needed to check for changes rather than try to implement its own caching, make a bunch of redundant API calls, or just hope there's been no change.

What do you think?

[fayland]

@schwern please go ahead.

let me know if you want to be a co-maintainer.

Thanks.