Filter Bank

Starting to implement filter bank. Using the 2 filters w/ impulse
responses stated in Martinez paper. Also renamed fft.m to fft_check.m to
prevent issues with naming
First scale of wavelet transform implemented

DWT of signal calculated and plotted. 0 crossings correspond to local
minimum/maximum
Implemented multiple Scales

Bug: Zero-crossings on scales are being shifted further to right. Not
lining up with actual local min/max. Is this right? We need to check
papers to find out

Also, I have not implemented decimation... I'm wondering if the mallat's
algo will differ depending on which platform you use (C vs Matlab).