Make when to sync configurable

[robnasby]

First off, awesome cookbook. It almost does exactly what I need... 😉

At our company, we only perform chef-client runs at specific times (e.g. when migrating software). Therefore, the repo sync being performed as part of the chef-client run doesn't work well for us. We would prefer the ability to schedule the sync using cron. With scheduled syncing, we would also prefer to disable the sync during the chef-client run.

I've been working on a PR to add this functionality, but wanted to gauge your interest before I get too far into it.