Merge pull request #70 from reaperhulk/master

readme updates [ci skip]
Add #remove_list_entry to ReaderWriter. Fixes #68

Reminder: the FileReaderWriter class is subject to inherent race
conditions if you run more than one process that touches it. It is
recommended that you replace it with a subclass using a database.
Merge pull request #71 from reaperhulk/fix-68

Add #remove_list_entry to ReaderWriter. Fixes #68