class Build::Files::State

def initialize(files)

@raises [ArgumentError] If files is not a Files::List.
@parameter files [List] The list of files to track.
Initialize file state tracking. 
def initialize(files)
	raise ArgumentError.new("Invalid files list: #{files}") unless Files::List === files
	
	@files = files
	
	@times = {}
	
	update!
end