Unpin gunicorn.

requirements/edx/base.in

@@ -94,7 +94,7 @@ firebase-token-generator==1.3.2
 fs==2.0.18
 fs-s3fs==0.1.8
 glob2                               # Enhanced glob module, used in openedx.core.lib.rooted_paths
-gunicorn==19.5.0
+gunicorn
 help-tokens
 html5lib                            # HTML parser, used for capa problems
 ipaddress                           # Ip network support for Embargo feature

requirements/edx/base.txt

@@ -132,7 +132,7 @@ future==0.17.1            # via pyjwkest
 futures==3.2.0 ; python_version == "2.7"  # via django-pipeline, python-swiftclient, s3transfer, xblock-utils
 geoip2==2.9.0
 glob2==0.7
-gunicorn==19.5.0
+gunicorn==19.9.0
 help-tokens==1.0.4
 html5lib==1.0.1
 httplib2==0.13.0          # via oauth2, zendesk

requirements/edx/development.txt

@@ -165,7 +165,7 @@ future==0.17.1
 futures==3.2.0 ; python_version == "2.7"
 geoip2==2.9.0
 glob2==0.7
-gunicorn==19.5.0
+gunicorn==19.9.0
 help-tokens==1.0.4
 html5lib==1.0.1
 httplib2==0.13.0

requirements/edx/testing.txt

@@ -160,7 +160,7 @@ future==0.17.1
 futures==3.2.0 ; python_version == "2.7"
 geoip2==2.9.0
 glob2==0.7
-gunicorn==19.5.0
+gunicorn==19.9.0
 help-tokens==1.0.4
 html5lib==1.0.1
 httplib2==0.13.0