Add tests for TOML formatting style

[sjlongland]

As mentioned in PR #112, it'd be good to add a check to see that the default format more-or-less matches typical formatting styles used in the setuptools documentation; notably fields like license and authors use the inline table format where possible, as this is the style generally used in setuptools documentation.

[diazona]

(I edited in a space, otherwise it doesn't autolink the PR)