Sorting is left to the template (using Jinja's sort filter).

Signed-off-by: Chamon <[luizchamon] [gmail]>
Updated the keeponly function to work on any field (at least while Jinja's equalto doesn't make it to the release version).

Signed-off-by: Chamon <[luizchamon] [gmail]>
Update example (include new keeponly function and sort filters).

Signed-off-by: Chamon <[luizchamon] [gmail]>
Update README.

Signed-off-by: Chamon <[luizchamon] [gmail]>