Fix code to work with Ruby 1.9
Fix code to work with Ruby 1.9

* In 1.9 anonymous classes have a nil name instead of an empty string, so make
  sure that the name passed in to IceNine::Freezer[] is stringified.
* Specify that Module#const_defined? and Module#const_get do not search the
  ancestor classes when doing constant lookup. This allows the freezer class
  lookup to stay scoped under the IceNine::Freezer namespace.

dkubb/ice_nine,soulcutter/ice_nine,nepalez/ice_nine