Better layout for limits doc page

[jantman]

https://awslimitchecker.readthedocs.io/en/latest/limits.html has a confusing layout... it's easy to look under the TrustedAdvisor or API sections, see a bunch of headings, think that's it, and not look farther down the page.

Get rid of the dedicated TrustedAdvisor and API sections at the top of the page, and make the service names themselves the top-level headers. Put a little description about Trusted Advisor and APIs at the top of the page. Then, change the tables under each service section to have 4 columns: Name, TA, API, Default ... and link the TA and API column headers to the notes at the top of the page.

Hopefully this will make it more clear.

So, we're looking for something like:

Limit Name	TA	API	Default Limit
foo	yes	yes	1
bar		yes	200
baz			333

[jantman]

This has been released just now in 4.0.0, which is now live on PyPI.