Only update index when forced

When working on another plugin I noticed this one updating its index in the background. This patch should keep that from happening.

Pretty print index

Text editors wouldn’t open a massive one-line JSON, so I added new lines to the index. No changes to search functionality.

Fix corrupt gzips

This release fixes #2, among others (see Changelog for a full list).

Update to Python 3

Although this plugin is still nowhere near production-ready, it should now work in calibre v5. (It broke because it wasn’t prepared for the switch to Python 3. Now it is.)

Nowhere near stable

But we have to start somewhere, right? Make sure to report all your issues on the “Issues” tab, so we can work on fixing them for a next release.