yamll: yaml linter

Run this over YAML files to determine if they are well-formed or not.

Usage: yamll [-hq] files...

        For each file, yamll will make sure it is a well-formatted YAML
        file.  Unless the -q option is passed, yamll will print the names
        of each file and whether it was well-formed. With the -q option,
        only malformed files are printed.

	If the only command line argument is "-", yamll will read from
	standard input. It is assumed the entirety of standard input is
	a single file.