nbconvert and new templates

[dpshelio]

nbconvert is used to generate the htmls for the website. However, they've changed how to distribute the templates and the files we try to extend basic.tpl in
https://github.com/UCL-RITS/doctoral-programming-intro/blob/fef8926c442d18b576f891243c94c40aef4fd9b5/jekyll.tpl#L1
is not available anymore.
nbconvert, therefore, has been pinned in #17.

Templates Cookbook

[ageorgou]

See similar issue with a bit more info (though may be out of date): UCL/rsd-engineeringcourse#186

[ageorgou]

One possible solution in UCL/rsd-engineeringcourse#214.