v1.0.0: Improved error handling, user-defined serialization

This is the first release under the dlang-community banner.

It features a few internal improvements, doc fixes,
as well as the following major changes since the last release (v0.19.1):

• ensureNotInGC will no longer allocate (#70);
• toString(sink) or toString will now be used for serialization if found on an aggregate (#68);
• Every SqliteException instance now has an error code (#60);
• VariantException will no longer be catched and wrapped in an SqliteException (#60);