Merge pull request #1 from pnc/master

Truncate seconds when formatting modified dates (FTP don't care)
Catch errors during RETR and respond with a 550 before actually starting the data connection to prevent corrupt files on the client side.
Update README a bit.
"fix" a brittle test.
Remove unused lambda parameter
Freeze meck version (they have made breaking changes)
Fix test suite: receive function for stor is now arity 0
Fix memory/performance issue in example server