Update Windows Requirements & CI

- Merge windows requirements into requirements.txt and requirements-extra.txt
- Update tox.ini to always use build.py
- Update build.py to have module only option
- Update tox.ini to text python 3.9
- Update .travis.yml to test 3.8 and 3.9 on newer Ubuntu LTS
-Update .travis.yml to work with changes to windows tox
(also update windows to 3.8)

tox.ini

@@ -1,35 +1,19 @@
 [tox]
-envlist = style,py36,py37,py38
+envlist = py36,py37,py38,py39
 skipsdist = True
 skip_missing_interpreters = True
 
 [testenv]
-whitelist_externals =
-    make
 setenv =
     PYTHON="{envpython}"
 commands =
-    make modules
-    py.test core hscommon
+    python build.py --modules
+    flake8
+    {posargs:py.test core hscommon}
 deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/requirements-extra.txt
 
-[testenv:style]
-deps =
-    {[testenv]deps}
-    flake8
-commands =
-    flake8
-
-[testenv:WINDOWS]
-deps =
-    {[testenv]deps}
-    -r{toxinidir}/requirements-windows.txt
-commands =
-    python build.py
-    python package.py
-
 [flake8]
 exclude = .tox,env,build,cocoalib,cocoa,help,./qt/dg_rc.py,cocoa/run_template.py,./pkg
 max-line-length = 120