Various stylist changes to make flake8 happy
Make the code compatible with Python 3
Correct the low-pass/high-pass plot labels

Correct the low-pass and high-pass plot labels, which were switched around.
Correct the order of edge frequencies

The filters in the H and AP properties are sorted from highest to lowest
frequencies, so make sure the order of the frequencies in the edge_freqs
property matches.
Make the import style conform to PEP 8
Make the plot labels consistent
Improve the plots
Minor stylistic change
Use relative imports within the package
regalia_mitra is a module, not a package
Import RMFilterBank directly into filter_banks

Rather than simply import the regalia_mitra module, import the RMFilterBank
class directly.
Add a TODO entry