moved demos to subdirectory

diff --git a/python/demo_filterbank_slaney.py b/python/demos/demo_filterbank_slaney.py
similarity index 100%
rename from python/demo_filterbank_slaney.py
rename to python/demos/demo_filterbank_slaney.py

diff --git a/python/demo_filterbank_triangle_bands.py b/python/demos/demo_filterbank_triangle_bands.py
similarity index 100%
rename from python/demo_filterbank_triangle_bands.py
rename to python/demos/demo_filterbank_triangle_bands.py