Update with v6.3

[augustfly]

This updates the files to v6.3 on GitHub (original release on July 10, 2019).

@gregschwarz We need to make a list of which issues are closed by this PR. The AASTeX history page doesn't have the updated feature/bugs listed yet for v6.3 so I'm not clear on which are closed. Once we know about them I can add them to the list below so they will auto close when you accept the PR. These are the ones I'm sure about:

closes #56
closes #57
closes #63
closes #68
closes #70
closes #72
closes #74
closes #75
closes #76
closes #77
closes #78
closes #81

I tried looking through the CLS file for documentation of which issues were closed, but I couldn't find enough detail in Amy's comments to make me 100% sure of anything.

[augustfly]

Here is my "I think" list of issues to be closed. Let me know if I'm right so I can add them above or if I'm wrong before you accept the PR. Of course add more if you know about them.

closes #72 : enforces TOC for accessibility
closes #74 : I hope? This is a nasty little bug.
closes #76 : by accepting the solution already implemented in PR 79
closes #81 : i see a modification of the table note mark style in the new CLS.
closes #83 : I thought we'd discuss this extensively.

[augustfly]

@gregschwarz Can you go through the AASTeX repo issues and list (in this thread) which ones are closed by v6.3? Then I'll update the pull request thread and have you accept the PR. I can go through them after that and finalize any more that are outstanding.

[gregschwarz]

I can confirm that all of the issues mentioned in this thread are addressed in v6.3 with two exceptions. Issue #61 is a conflict between v6.2 and the siunitx.sty package. These can be tricky as common names can be used in different packages, in this case \tablenum, and there is no way to anticipate what will conflict with AASTeX. In the new v6.3 author guide we have some help for authors that run into this specific siunitx.sty problem.

We will continue to document other solutions as they arise. The other exception is issue #83 which unfortunately I forgot to add to the requirements page that was sent to our LaTeX programmer. We should keep this open for the next version.

[augustfly]

Okay, I will manually comment on #61 and #83 after we merge. I think you can go ahead @gregschwarz