Another fix to the docstrings, this time for the English part of the
docstrings, not the Python class name. No functional changes here.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
This moves away from the deprecated notmuch_database_add_message API
and instead uses the notmuch_database_index_file API. This means
instroducing a class to manage the index options and bumping the
library version requirement to 5.1.
