Use tables in README?

[elsiehupp]

I found the existing README to be somewhat difficult to visually parse, so I tried formatting the commands and return values in tables to make them somewhat clearer.

The two issues I'm stuck on are:

1. reStructuredText doesn't like that I'm reusing the headline "First:", but it only generates a warning, not an error. This is probably not a breaking issue.
2. GitHub doesn't seem to respect the inline code-syntax highlighting I used within the table cells. GitHub seemingly only respects block-level code-syntax highlighting, and table cells in neither reStructuredText nor Markdown support blocks.

For problem No. 2, I don't know how the README renders on PyPI, but if PyPI has the same problem it might be worth using more conventional API formatting, like, e.g., the official Python documentation has.

I would be happy to iterate on this pull request if necessary.