Add final psets and project

Gemfile

Gemfile.lock

_notes/fourier_examples.md

_notes/fourier_series.md

_notes/fourier_transform.md

_psets/01.md

_psets/02.md

_psets/03.md

_psets/04.md

_psets/05.md

_psets/06.md

_psets/07.md

_psets/08.md

_psets/09.md

_psets/10.md

_psets/11.md

_psets/12.md

_sass/main.scss

assets/img/notes_ft_examples_1.jpg

assets/img/notes_ft_examples_2.jpg