Bump Celery and kombu versions for Python 3.7

See celery/kombu#841

requirements.txt

@@ -1,7 +1,7 @@
-amqp==2.2.2
+amqp==2.5.2
 aniso8601==1.2.1
-billiard==3.5.0.3
-celery==4.1.0
+billiard==3.6.2.0
+celery==4.4.0
 certifi==2017.7.27.1
 chardet==3.0.4
 ciscosparkapi==0.6.1
@@ -13,9 +13,10 @@ funcsigs==1.0.2
 future==0.16.0
 gunicorn==19.7.1
 idna==2.5
+importlib-metadata==1.5.0
 itsdangerous==0.24
 Jinja2==2.10.1
-kombu==4.1.0
+kombu==4.6.7
 MarkupSafe==1.0
 mock==2.0.0
 pbr==3.1.1
@@ -26,5 +27,6 @@ requests==2.21.0
 requests-toolbelt==0.8.0
 six==1.10.0
 urllib3==1.24.2
-vine==1.1.4
+vine==1.3.0
 Werkzeug==0.14.1
+zipp==2.1.0