[enh] #225: Install pytest-asyncio as a dev depedency

Pipfile

@@ -21,6 +21,7 @@ twine = "*"
 pytest = "*"
 coverage = "*"
 pytest-cov = "*"
+pytest-asyncio = "*"
 
 [requires]
 python_version = "3.7"

Pipfile.lock

 {
     "_meta": {
         "hash": {
-            "sha256": "715966131dae907b8cc33f3e33648a9e924b69c584b4c62b82006d6a83f3727d"
+            "sha256": "f25235dfd1a2dae80f3d1fd761ecb23ad6f6d7ca46e758d51b3498a995afc483"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -481,6 +481,14 @@
             "index": "pypi",
             "version": "==4.4.2"
         },
+        "pytest-asyncio": {
+            "hashes": [
+                "sha256:9fac5100fd716cbecf6ef89233e8590a4ad61d729d1732e0a96b84182df1daaf",
+                "sha256:d734718e25cfc32d2bf78d346e99d33724deeba774cc4afdf491530c6184b63b"
+            ],
+            "index": "pypi",
+            "version": "==0.10.0"
+        },
         "pytest-cov": {
             "hashes": [
                 "sha256:2b097cde81a302e1047331b48cadacf23577e431b61e9c6f49a1170bbe3d3da6",