Changes to polarization ASAD method

[eneights]

Some changes suggested by @israelmcmc based on PR #240:

• Replace calculate_uncertainties() with sqrt(counts) and histpy's bin_error
• Store ASADs as histpy Histogram objects
• Exclude errors in response from error propagation
• Move calculate_azimuthal_scattering_angle() to PolarizationAngle class
• Make it possible for user to initialize PolarizationASAD object and immediately run fit()
• Run profiler and optimize code (currently, use project() just to get number of bins, use for loops for operations that can be parallelized, and repeat operation within a loop that could be cached)
• Replace fit to constant() function with np.mean()
• Don't generate plots by default
• Use logging instead of print statements