rename file
split unit tests
add more test case
added more test cases
added test case for skip and limit
improve performance by cache the document on _apply_query()
fix skip bug
modernized code
Assumed Maintainership
set the journal mode to WAL
add test for ensure_index
remove support for python 2
support transaction if needed
code format
organize import
ignore html coverage
Update README.md
sorting on nested key
Update README.md
sorting documents by keys and directions