Updated error message when Vestige cannot find the specified default calendar (by --default)
Added idle reminder, which sounds the terminal bell after 2 minutes idle. --remind flag
Also added a function that defines whether or not the user is currently working.
Docs — Updated README.md to add --remind option
Docs — Update README.md to remove redundancy with the How and How does it work sections
Docs — Minor updates to README.md for clarity, and update Todo section