Autoformatting: PEP8 via black & blitz .rst trailing whitespace

[sadielbartholomew]

Close #16 and towards the closure of #17, though not closing the latter because here I have provided basic configuration for flake8 but not went through and addressed all of the errors and warnings it raises, which should be done in another PR since this one is pure (auto-)formatting and I don't want to mix in more significant changes.

In this PR I have:

• added files to configure black and flake8, using the same config. as cf-python (which I will review shortly in case we want to update it for both libraries);
• run black on all files in the codebase, via two commits (first for the cfplot directory for the main codebase, then anything else, mostly docs and setup files etc., by running from the repo root);
• removed a file temp.py which was in the codebase but shouldn't be, leftover from Andy's files, as evidenced by it failing to be valid Python and supported by the name 'temp';
• additionally removed all trailing whitespace in the .rst files that was raised by a nice tool called sphinx-lint, which I found because I was hoping to find a library that would allow me to apply black to the Python code snippets in the .rst but found this first and wanted to get rid of the vrey large amount of superfluous whitespace there first. I will investigate for a future PR on a possible black linter for the .rst Python snippets.

[sadielbartholomew]

This is all auto-formatting, with a large amount of line changes, so not suitable (read: would be tedious) for peer/code review, and I've applied sanity checks to ensure the code still runs fine after these (with new testing to come anyway), so I will merge.