Make target for building wheel (#1031)

* Add wheel make target

* Folders created when making wheels will be removed by clean target

* Simplifie wheel target

Replacing wheel build command from:
`python setup.py bdist_wheel` with:
`pip wheel . --no-deps`
This will have several advantages.

Use pyproject for dependencies. This makes it much cleaner to build
wheels.

We no longer need to check for the availability of the wheel package.
And the build will be out of source, and we don't need to cleanup
intermediate folders.

The `clean` target will now remove *.whl files in the root of the
project. This is where `make wheel` will output the wheels to with the
new command.

Makefile

@@ -1,5 +1,5 @@
 .PHONY: coverage test test_first_fail clean autopep8 lint doc-html \
-	python-version manifest lcov
+	python-version wheel manifest lcov
 
 # Special definition to handle Make from stripping newlines
 define newline
@@ -113,6 +113,7 @@ ifdef COV_PROG
 	@${COV_PROG} erase
 endif
 	@${MAKE_PROG} -C contrib/opentimelineio_contrib/adapters clean VERBOSE=$(VERBOSE)
+	rm -vf *.whl
 
 # conform all files to pep8 -- WILL CHANGE FILES IN PLACE
 # autopep8:
@@ -141,6 +142,10 @@ ifndef FLAKE8_PROG
 endif
 	@python -m flake8
 
+# build python wheel package for the available python version
+wheel:
+	@pip wheel . --no-deps
+
 # format all .h and .cpp files using clang-format
 format:
 	opentimeFiles = src/opentime/*.h src/opentime/*.cpp