Some additions

[FewKinG]

Hey there,

I made some changes to your active_column gem:

• I changed the requirement for the simple_uuid gem from ~> 0.1.0 to >= 0.1.0
• You can now use a block to define column metadata like this:
  create_column_family :Test do |cf|
  cf.column :mycolumn do |cd|
  cd.validation_class = :utf8
  end
  end
• Symbols for "comparator_type", "default_validation_class", "key_validation_class" are now correctly converted to COMPARATOR_TYPES strings.