Fix legacy functions and verbose

Closes #2 (closed)

Module API changes

• Turn off verbose for combining channels in load_dataset
• Fix verbose in process_epochs and epochs_viz
• Replace legacy functions to pick channels in process_epochs and epochs_viz
• Replace legacy parameters to get data from MNE epochs in process_epochs and epochs_viz
• Replace legacy function to plot power spectra in epochs_viz

Other changes

• Version number