README - warn about journal-vault relation in MUST READ section
README - move some entries from MUST READ to Limitations
Don't use flock LOCK_UN before file closing.

Althrough it might work well with autoflush(), it's considered
bad style and introduces bug without autoflush()

more info:
http://perl.plover.com/yak/flock/samples/slide004.html
http://perl.plover.com/yak/flock/samples/slide005.html