Major - Make path argument in wr.s3.to functions optional

[jaidisido]

Issue #, if available:
#586

Description of changes:
path argument is now optional. The code changes implementing this feature are based on the below logic tree:

if dataset is False:
	if path is None:
		raise Exception("you must pass `path`")
	else:
		no problem
else:
	if database and table are None:
		if path is None:
			raise Exception("you must pass `path`")
		else:
			no problem
	else:
		if path is None:
			if table exists:
				path = catalog_path
			else:
				raise Exception("you must pass `path`")
		else:
			if table exists:
				if path != catalog_path:
					raise Exception("`path` must be equal to catalog path")
			else:
				no problem

Added and modified s3 tests to evaluate impact

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jaidisido]

Clarified some code sections

[jaidisido]

Since path is now optional, it was removed from some tests to check that they still pass even without referencing it

[jaidisido]

In certain cases, Wrangler must throw an error if the path is missing or wrong

[igorborgest]

LGTM