starting moving feats to featx: a better feature retriever
Rename `make` to `common_path`, add `klass_var` for `common_path`
Remove klass_var
Redesign `common_path`, `stores_path`, with more flexibility
Add featx doc
Add featx base
Remove unnecessary klass_var in `save`
Add `force` option to `load`
Complete base feats functions
Refactor `slider`, remove `get_slide` method
Move featx to featx base
Add deletion function, resolve #74
Fix `img_path`(sp) recursive use bug
Add clear function to delete all files
Move featx to base
Make deletions work, #74
Refactor init in video
Add a methods to get frame ids
Change to use `featx` in package
Rename base `featx` to `feats`