Document Ruby 1.9 dependency

[temujin9]

Nobody at Infochimps uses 1.8 internally, and we lack a full test framework to ameliorate that. Therefore, we don't officially support Ruby 1.8, although we will happily accept pull requests aimed at keeping Ironfan working there as well.

Not 100% sure where this should end up; probably in the README. @mrflip, please chime in if you have other suggestions.

[mrflip]

Updated the READMEs; closing.

To anyone who wants to port:

• define_method in ironfan-pantry/cookbooks/silverware: 1.9 allows default and block parameters to a block. You'll have to change this to the string form of class_eval, calling def.
• realdirpath in the knife.rb
• I don't think there are occurrences of new-style hashes, BasicObject, or any assumptions that a hash is ordered.