v0.4.0

This release is focused on correctness and supporting as much as we can fit into a reasonable window. Search is here; there's a syntax in the readme. Fields have arrived, but are not very usable outside of search. Notifications are done as programmed, and aside from that, there has been a lot of work done on the google calendar end.

The unixfile format changed, so you will need to erase your DB if you went that option. If you strongly desire a converter, please ask in the issues, I'm happy to write one I just don't think there are many users.

Changelog:

-   Notifications are now durations; if they are not provided via `notify` entry clauses, they will not exist and you will not be notified. You can add notifications to existing calendar items with `edit`.
-   Many bugfixes to the MemoryDB implementation. **YOUR OLD MEMORYDB WILL NO LONGER WORK AND YOU SHOULD DELETE IT. FILE AN ISSUE IF YOU NEED A CONVERTER.**
-   Correct a problem where failing to load the DB (due to underlying data structure changes) would erase the DB's contents.
-   Support using day names for the following week of time. Please see the documentation under "Dates".
-   Add a parameter to allow the customization of the window used to query Google Calendar. `saturn config set-query-window`.
-   Fix issue with 24h time field preventing the configuration from being deserialized.
-   Errors that occur in `sui` are now much more consistent, easier to read,
    and should not make the program unusable.
-   Fixed another race condition plaguing launches of `$EDITOR` for edit commands in `sui`.
-   New search feature! See [README](README.md) for more.
-   `saturn dump` was renamed to `saturn show`. `dump` will be a new subcommand in the future.
-   Google Calendar notification settings are now honored.
-   Support fields in editor and google calendar implementations. Fields
    are now a map of string -> array of string and are shown in listing
    commands.
-   Fix an issue where all day tasks on sundays would not be shown
-   Several style changes to `sui`:
    -   Replaced underlining today's tasks with coloring them in bright
        white, using dark gray for all others.
    -   Highlighting in light green tasks that occur within the next hour.
-   Fix an issue where a bug would prevent recurring tasks from being entered into Google Calendar