Pipfile.lock: run pipenv update

Brings gunicorn 20.0.4, pytest 5.3.1, and others. I hadn't noticed
that gunicorn was bumped from 19.x.x to 20.x.x last week.

See: https://docs.gunicorn.org/en/stable/news.html#id6

Pipfile.lock

@@ -52,11 +52,11 @@
         },
         "gunicorn": {
             "hashes": [
-                "sha256:0806b5e8a2eb8ba9ac1be65d7b743ec896fc25f5d6cb16c5e051540157b315bb",
-                "sha256:ef69dea4814df95e64e3f40b47b7ffedc6911c5009233be9d01cfd0d14aa3f50"
+                "sha256:1904bb2b8a43658807108d59c3f3d56c2b6121a701161de0ddf9ad140073c626",
+                "sha256:cd4a810dd51bf497552cf3f863b575dabd73d6ad6a91075b65936b151cbf4f9c"
             ],
             "index": "pypi",
-            "version": "==20.0.0"
+            "version": "==20.0.4"
         },
         "idna": {
             "hashes": [
@@ -120,13 +120,6 @@
         }
     },
     "develop": {
-        "atomicwrites": {
-            "hashes": [
-                "sha256:03472c30eb2c5d1ba9227e4c2ca66ab8287fbfbbda3888aa93dc2e28fc6811b4",
-                "sha256:75a9445bac02d8d058d5e1fe689654ba5a6556a1dfd8ce6ec55a0ed79866cfa6"
-            ],
-            "version": "==1.3.0"
-        },
         "attrs": {
             "hashes": [
                 "sha256:08a96c641c3a74e44eb59afb61a24f2cb9f4d7188748e76ba4bb5edfa3cb7d1c",
@@ -230,10 +223,10 @@
         },
         "pluggy": {
             "hashes": [
-                "sha256:0db4b7601aae1d35b4a033282da476845aa19185c1e6964b25cf324b5e4ec3e6",
-                "sha256:fa5fa1622fa6dd5c030e9cad086fa19ef6a0cf6d7a2d12318e10cb49d6d68f34"
+                "sha256:15b2acde666561e1298d71b523007ed7364de07029219b604cf808bfa1c765b0",
+                "sha256:966c145cd83c96502c3c3868f50408687b38434af77734af1e9ca461a4081d2d"
             ],
-            "version": "==0.13.0"
+            "version": "==0.13.1"
         },
         "prompt-toolkit": {
             "hashes": [
@@ -273,10 +266,10 @@
         },
         "pygments": {
             "hashes": [
-                "sha256:71e430bc85c88a430f000ac1d9b331d2407f681d6f6aec95e8bcfbc3df5b0127",
-                "sha256:881c4c157e45f30af185c1ffe8d549d48ac9127433f2c380c24b84572ad66297"
+                "sha256:83ec6c6133ca6b529b7ff5aa826328fd14b5bb02a58c37f4f06384e96a0f94ab",
+                "sha256:b7949de3d396836085fea596998b135a22610bbcc4f2abfe9e448e44cbc58388"
             ],
-            "version": "==2.4.2"
+            "version": "==2.5.1"
         },
         "pyparsing": {
             "hashes": [
@@ -287,11 +280,11 @@
         },
         "pytest": {
             "hashes": [
-                "sha256:15837d2880cb94821087bc07476892ea740696b20e90288fd6c19e44b435abdb",
-                "sha256:b6cf7ad9064049ee486586b3a0ddd70dc5136c40e1147e7d286efd77ba66c5eb"
+                "sha256:63344a2e3bce2e4d522fd62b4fdebb647c019f1f9e4ca075debbd13219db4418",
+                "sha256:f67403f33b2b1d25a6756184077394167fe5e2f9d8bdaab30707d19ccec35427"
             ],
             "index": "pypi",
-            "version": "==5.2.3"
+            "version": "==5.3.1"
         },
         "six": {
             "hashes": [