Update dependencies.

package.json

@@ -17,28 +17,28 @@
   "devDependencies": {
     "browserify": "^16.1.0",
     "commander": "^2.20.0",
-    "cross-env": "^5.1.3",
+    "cross-env": "^5.2.1",
     "eslint": "^5.16.0",
-    "eslint-config-digitalbazaar": "^2.0.0",
+    "eslint-config-digitalbazaar": "^2.2.0",
     "express": "^4.16.2",
-    "karma": "^3.1.4",
-    "karma-browserify": "^6.0.0",
-    "karma-chrome-launcher": "^2.2.0",
+    "karma": "^4.4.1",
+    "karma-browserify": "^7.0.0",
+    "karma-chrome-launcher": "^3.1.0",
     "karma-edge-launcher": "^0.4.2",
-    "karma-firefox-launcher": "^1.1.0",
+    "karma-firefox-launcher": "^1.3.0",
     "karma-ie-launcher": "^1.0.0",
     "karma-mocha": "^1.3.0",
     "karma-mocha-reporter": "^2.2.5",
     "karma-safari-launcher": "^1.0.0",
-    "karma-sauce-launcher": "^1.2.0",
+    "karma-sauce-launcher": "^2.0.2",
     "karma-sourcemap-loader": "^0.3.7",
     "karma-tap-reporter": "0.0.6",
-    "karma-webpack": "^3.0.5",
+    "karma-webpack": "^4.0.2",
     "mocha": "^5.2.0",
     "mocha-lcov-reporter": "^1.2.0",
     "nodejs-websocket": "^1.7.1",
-    "nyc": "^14.1.1",
-    "opts": "^1.2.2",
+    "nyc": "^15.0.0",
+    "opts": "^1.2.7",
     "webpack": "^3.11.0",
     "worker-loader": "^2.0.0"
   },