feature/added signals transformation and meaviewer

[igorcantele]

Added signal transformations (i.e. Energy, Amplitude, Variance, Raw, Shutter)
Added meaviwer to easily display data

Tests not implemented yet
Documentation not updated yet

[igorcantele]

def func(data, mask):
    return data[~mask]

callable = func

amplitude = bwpy.signal.amplitude(slice, 100)
artifacts = bwpy.signal.detect_artifacts(amplitude)
amplitude_data = amplitude.data
shutter = bwpy.signal.shutter(artifacts, amplitude_data, 200, callable)
mea_viewer.MEAViewer().build_view(
    file, slice=shutter, view_method="amplitude", bin_size=10
).show()

Example of flow:

• Computing the amplitude of a time slice, in order to get amplitude_data.
• Detecting artifacts indexes with detect_artifacts.
• Plotting all the artifacts in a HTML page with shutter and cutting them with the callback function.
• Using MEAViewer to display normal activity without artifacts.

[Helveg]

Nice new features :)