standardize and test data loading

[9q9q]

thanks @cshewmake2 for adding a bunch of stuff at sparsecoding/data, would be cool to build this up more and use across all notebooks to avoid headaches with data consistency or path stuff (i can help)

[belsten]

@9q9q what is the status of this? Can this be closed?

[9q9q]

not being used yet in notebooks, and no tests yet. i'll take this on