Missing classifiers for Python 3.8/3.9

[samlishak-artemis]

Python 3.8 and 3.9 are missing from the classifiers in setup.py:

dash/setup.py

Lines 55 to 63 in 358c508

	"Programming Language :: Python",
	"Programming Language :: Python :: 2",
	"Programming Language :: Python :: 2.7",
	"Programming Language :: Python :: 3",
	"Programming Language :: Python :: 3.3",
	"Programming Language :: Python :: 3.4",
	"Programming Language :: Python :: 3.5",
	"Programming Language :: Python :: 3.6",
	"Programming Language :: Python :: 3.7",

But there is no restriction to 3.7 or below in python_requires:

dash/setup.py

Line 29 in 358c508

python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*",

Anecdotally, I've been using Dash on Python 3.9 with no issues. Reporting as an issue as I can't see any mention of Python 3.8 and 3.9 compatibility so far!

[alexcjohnson]

Good call, the classifiers haven't been updated in a while. FYI in the upcoming Dash 2.0 we're planning to change python_requires to ">=3.6" - dropping Py2 altogether as well as 3.5 and below.

[samlishak-artemis]

I can submit a basic PR to add 3.8 and 3.9 if you like? Not a big job, but it's something 😄

[samlishak-artemis]

Never mind, looks like you beat me to it - thanks very much!