Make emulateapj obsolete about aastex52

[augustfly]

The new version of AASTeX (v6.0) was built off of emulateapj with permission of the authors/maintainers. I'd like to consider this request closed, @jradavenport

[augustfly]

Our plan for AASTeX TNG is make the default PDF compilation match the final ApJ template as closely as possible. There are lots of reasons for this, which you might guess:

• referees really want this version bc it is so much easier to read;
• it transfers the authors layout requests to IOP project better than any Readme file could;
• it normalizes preprint version look and feel for everyone.

[jradavenport]

Agreed! Awesome!