Bump superagent from 3.6.3 to 3.8.3

Bumps [superagent](https://github.com/visionmedia/superagent) from 3.6.3 to 3.8.3.
- [Release notes](https://github.com/visionmedia/superagent/releases)
- [Changelog](https://github.com/visionmedia/superagent/blob/master/HISTORY.md)
- [Commits](https://github.com/visionmedia/superagent/compare/v3.6.3...v3.8.3)

Signed-off-by: dependabot[bot] <support@github.com>

package-lock.json

@@ -532,12 +532,6 @@
         "mime-types": "^2.1.12"
       }
     },
-    "formidable": {
-      "version": "1.1.1",
-      "resolved": "https://registry.npmjs.org/formidable/-/formidable-1.1.1.tgz",
-      "integrity": "sha1-lriIb3w8NQi5Mta9cMTTqI818ak=",
-      "dev": true
-    },
     "forwarded": {
       "version": "0.1.2",
       "resolved": "https://registry.npmjs.org/forwarded/-/forwarded-0.1.2.tgz",
@@ -1301,9 +1295,9 @@
       "dev": true
     },
     "superagent": {
-      "version": "3.6.3",
+      "version": "3.8.3",
-      "resolved": "https://registry.npmjs.org/superagent/-/superagent-3.6.3.tgz",
+      "resolved": "https://registry.npmjs.org/superagent/-/superagent-3.8.3.tgz",
-      "integrity": "sha512-GjsfCFijfjqoz2tRiStSOoTdy7gNZOcK3ar4zONP9D8dXQWE+Qg7cbePHimRpapo06WUvoU3dmgi2e4q+sab5A==",
+      "integrity": "sha512-GLQtLMCoEIK4eDv6OGtkOoSMt3D+oq0y3dsxMuYuDvaNUvuT8eFBuLmfR0iYYzHC1e8hpzC6ZsxbuP6DIalMFA==",
       "dev": true,
       "requires": {
         "component-emitter": "^1.2.0",
@@ -1311,20 +1305,62 @@
         "debug": "^3.1.0",
         "extend": "^3.0.0",
         "form-data": "^2.3.1",
-        "formidable": "^1.1.1",
+        "formidable": "^1.2.0",
         "methods": "^1.1.1",
         "mime": "^1.4.1",
         "qs": "^6.5.1",
-        "readable-stream": "^2.0.5"
+        "readable-stream": "^2.3.5"
       },
       "dependencies": {
         "debug": {
-          "version": "3.1.0",
+          "version": "3.2.6",
-          "resolved": "https://registry.npmjs.org/debug/-/debug-3.1.0.tgz",
+          "resolved": "https://registry.npmjs.org/debug/-/debug-3.2.6.tgz",
-          "integrity": "sha512-OX8XqP7/1a9cqkxYw2yXss15f26NKWBpDXQd0/uK/KPqdQhxbPa994hnzjcE2VqQpDslf55723cKPUOGSmMY3g==",
+          "integrity": "sha512-mel+jf7nrtEl5Pn1Qx46zARXKDpBbvzezse7p7LqINmdoIk8PYP5SySaxEmYv6TZ0JyEKA1hsCId6DIhgITtWQ==",
           "dev": true,
           "requires": {
-            "ms": "2.0.0"
+            "ms": "^2.1.1"
+          }
+        },
+        "formidable": {
+          "version": "1.2.1",
+          "resolved": "https://registry.npmjs.org/formidable/-/formidable-1.2.1.tgz",
+          "integrity": "sha512-Fs9VRguL0gqGHkXS5GQiMCr1VhZBxz0JnJs4JmMp/2jL18Fmbzvv7vOFRU+U8TBkHEE/CX1qDXzJplVULgsLeg==",
+          "dev": true
+        },
+        "ms": {
+          "version": "2.1.2",
+          "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz",
+          "integrity": "sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w==",
+          "dev": true
+        },
+        "process-nextick-args": {
+          "version": "2.0.1",
+          "resolved": "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-2.0.1.tgz",
+          "integrity": "sha512-3ouUOpQhtgrbOa17J7+uxOTpITYWaGP7/AhoR3+A+/1e9skrzelGi/dXzEYyvbxubEF6Wn2ypscTKiKJFFn1ag==",
+          "dev": true
+        },
+        "readable-stream": {
+          "version": "2.3.6",
+          "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.6.tgz",
+          "integrity": "sha512-tQtKA9WIAhBF3+VLAseyMqZeBjW0AHJoxOtYqSUZNJxauErmLbVm2FW1y+J/YA9dUrAC39ITejlZWhVIwawkKw==",
+          "dev": true,
+          "requires": {
+            "core-util-is": "~1.0.0",
+            "inherits": "~2.0.3",
+            "isarray": "~1.0.0",
+            "process-nextick-args": "~2.0.0",
+            "safe-buffer": "~5.1.1",
+            "string_decoder": "~1.1.1",
+            "util-deprecate": "~1.0.1"
+          }
+        },
+        "string_decoder": {
+          "version": "1.1.1",
+          "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.1.1.tgz",
+          "integrity": "sha512-n/ShnvDi6FHbbVfviro+WojiFzv+s8MPMHBczVePfUpDJLwoLT0ht1l4YwBCbi8pJAveEEdnkHyPyTP/mzRfwg==",
+          "dev": true,
+          "requires": {
+            "safe-buffer": "~5.1.0"
           }
         }
       }