Update ReadTheDocs Theme

[trevorb1]

The readthedocs page uses the default theme (Alabaster) which is a little hard to read (particularly in the api reference section). The available themes are shown here. I personally like the book theme, but Im not really that picky.

When updating the theme, you will need to upate the conf.py file and add the accompanying library to requirement files.

delta-e-utils/docs/conf.py

Lines 182 to 184 in df40307

	# The theme to use for HTML and HTML Help pages. See the documentation for
	# a list of builtin themes.
	html_theme = "alabaster"

Successful PR for this issue will include:

• A new readthedocs theme

[trevorb1]

Maybe relates to issue #34