general cleanup: copyright, license, Readme.md, closes #5

COPYING.txt

README.md

src/fetch_series.m

src/fetch_series_by_api_link.m

src/fetch_series_page.m

src/filter_series.m

src/flatten_dbnomics_series.m

src/flatten_editor_series.m

src/iter_filtered_series.m

src/iter_series_info.m

src/normalize_period.m

src/normalize_value.m