Net http response refactoring

[myronmarston]

I refactored my implementation of the Net::HTTPResponse extension module to be far simpler, and thought you might want what I wound up with :).

[myronmarston]

Actually, hold off on this for now. I think I discovered some edge cases that neither the original code nor this refactoring handle properly. I'll let you know once I've figured it out.

[myronmarston]

OK, I made a minor change and pushed it here:

http://github.com/myronmarston/webmock/commit/f3cf8a2a24838e50eba4f0da9acf3b0eb0904f1e

Besides the simplification, this addresses a minor issue with making a HEAD request and reading the response with a block and #read_body.

[bblimke]

Thanks Myron. I like it :) Merged.