…odule that incorporates additional sketching aglorithms

… to finish

Work in progress. ``sketch`` module is implemented, but old
compatibility funcitons in ``sketch.range_finders`` still need to be
phased out.

Still need to better incorporate within random methods, perhaps giving
transform options. Also still need to standardize parameter names.

Additionally, single_pass methods have been depricated (masked with a
single subspace iteration) for now because the previous implementation
was not in fact 'single_pass'.

For the most part package now conforms with PEP parameter name
guidelines.

Still to do:
- `pca` : factor pca/spca/robspca
- `nmf` : factor and PEP parameter name eval
- `sketch` : ensure row wise sketches are indeed row wise and write
numerical accuracy checking tests

Additionally, in general there can be a lot of improvement as far as
code reproduction reduction in the testing modules.

The calling of `perform_subspace_iterations` now resides outside of the
transform functions so that it can be used independent of which
transform is used.

Additionally, default n_subspace has been set to 2.