Repeating events

Fix for #13 

Note, this doesn't take into account more complicated "every" date_strings like: "every 5 days starting next monday" or "every 2nd monday". Both those cases would see the word monday and make it so the daily is active every Monday, which may not be what is desired since that'll result in hp loss on Monday if it's not checked.

Thought this would be a good way to get this started though.
If a match is found, it returns an array with details about the match. If a match is not found it returns null.

The the `!!` is to trick it into being a boolean and is equivalent to `(item.todoist.date_string.match(/s($| |,|u)/i) && true) || false`