update docker setup and dependencies

setup.py

@@ -14,13 +14,13 @@ with open(os.path.join(PYTHON_DIR, 'VERSION'), 'r') as f:
 setuptools.setup(
     name="archivebox",
     version=VERSION,
+    license='MIT',
     author="Nick Sweeting",
     author_email="git@nicksweeting.com",
     description="The self-hosted internet archive.",
     long_description=README,
     long_description_content_type="text/markdown",
     url="https://github.com/pirate/ArchiveBox",
-    license='MIT',
     project_urls={
         'Donate': 'https://github.com/pirate/ArchiveBox/wiki/Donations',
         'Changelog': 'https://github.com/pirate/ArchiveBox/wiki/Changelog',
@@ -31,14 +31,14 @@ setuptools.setup(
         'Documentation': 'https://github.com/pirate/ArchiveBox/Wiki',
     },
     packages=setuptools.find_packages(),
-    python_requires='>=3.6',
+    python_requires='>=3.7',
     install_requires=[
         "dataclasses==0.6",
-        "mypy-extensions==0.4.1",
+        "mypy-extensions==0.4.3",
         "base32-crockford==0.3.0",
-        "django==2.2",
-        "django-extensions==2.1.6",
-        "python-crontab==2.3.6",
+        "django==3.0.7",
+        "django-extensions==2.2.9",
+        "python-crontab==2.5.1",
         "youtube-dl",
         "ipython",