Support default_proc in Ruby 1.8.x; refactor loading from YAML; whitespace munching

Monkeypath Hash to add default_proc support (pretty much stolen from https://github.com/findchris/typhoeus/commit/4ce19b10124026a4380617ba41d2be6b20d5f4a1 ).

Refactor the way an object is loaded from a YAML string or file.

Added and munched a little bit of whitespace here and there (couldn't help myself :) ).

Feel free to toss this if you don't want it.