A simpler, more limited fix to issue 4111.

Just change a few stray invocations of iteritems() to items(), in
order to be compatible with Python3 and consistent with previous
changes for supporting a Python2/3 unified source.

	modified:   sympy/core/compatibility.py
	modified:   sympy/core/tests/test_compatibility.py
	modified:   sympy/functions/elementary/trigonometric.py
	modified:   sympy/polys/polycontext.py
Change docstring to inline comment

This is in response to comment from smichr

	modified:   sympy/core/tests/test_compatibility.py
Merge pull request #2645 from rathmann/4111_iteritems_small

A simpler, more limited fix to issue 4111.
Allow enabling draft mode from GitHub_release
Write guide on uploading in the release README
Make GitHub_release part of the upload command
Merge branch '0.7.4' of github.com:sympy/sympy into 0.7.4
Change version to 0.7.4 (final)
Merge pull request #2644 from jrioux/tests

Fix slow tests in python3.