output deprecation warnings
ActsAsSplittable::Attributes + ActiveModel::Dirty
rename *_changed? to *_synced?
change format of deprecation warnings
rename *_synced? to *_unsynced? and define *_synced? ( ◜◡‾)<Oops..
add new features with ActiveModel::Dirty
update README.md
a little refactoring
call super in initialize_copy
reset changes after initialize
suppress ActiveModel::MissingAttributeError when select columns