Delegation issues in HTTP::Request::Caching

[headius]

While investigating jruby/jruby#3151, a few issues with the way Caching does delegation came to light:

• At least one place, in conditional_on_changes_to, an HTTP::Request object gets double-delegated. Both the self.class.new and .caching calls wrap the new HTTP::Request object in a delegating Caching instance.
• The Caching class itself is created before HTTP::Request has completed loading, resulting in a DelegateClass that does most delegation through method_missing rather than through generated, direct delegation methods.

These issues are not strictly bugs, but they likely affect performance. In the case of jruby/jruby#3151, they also exposed an obscure bug in JRuby.

[tarcieri]

I'm not really happy with the quality of the caching code. It's caused a lot of sporadic test failures. Having a dependency on rack isn't really something I like either.

Perhaps we could remove it and add it back when/if it's in a better state?

[zanker]

I agree with removing the code until something better is done.

[ixti]

👍 for wiping it out.

[tarcieri]

Created #240 to revert caching