chore: upgrade to new favicons version

BREAKING CHANGE: drop support for node versions < 8 to be able to upgrade favicons

.node-version

@@ -1 +1 @@
-10.14.0
+8.9.4

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 node_js:
-- '6'
+- '8'
 - node
 
 os:

package.json

@@ -40,33 +40,37 @@
   },
   "homepage": "https://github.com/jantimon/favicons-webpack-plugin",
   "devDependencies": {
-    "ava": "^1.4.1",
+    "ava": "^2.4.0",
     "commitizen": "4.0.3",
     "cz-conventional-changelog": "3.0.2",
-    "fs-extra": "^8.0.1",
+    "fs-extra": "^8.1.0",
     "html-webpack-plugin": "^3.2.0",
-    "nyc": "^14.1.1",
-    "standard-version": "7.0.0",
+    "image-size": "0.8.3",
+    "nyc": "^15.0.0",
+    "standard-version": "7.0.1",
     "webpack": "^4.35.0",
-    "webpack-cli": "^3.3.5",
-    "webpack-dev-server": "^3.7.2",
-    "webpack-merge": "^4.2.1"
+    "webpack-cli": "^3.3.10",
+    "webpack-dev-server": "^3.10.1",
+    "webpack-merge": "^4.2.2"
   },
   "dependencies": {
-    "cache-loader": "^3.0.1",
+    "cache-loader": "^4.1.0",
     "camelcase": "^5.3.1",
-    "favicons": "5.4.1",
-    "find-cache-dir": "^2.1.0",
+    "favicons": "5.5.0",
+    "find-cache-dir": "^3.2.0",
     "find-root": "^1.1.0",
     "loader-utils": "^1.2.3",
     "parse-author": "^2.0.0"
   },
   "peerDependencies": {
-    "webpack": "^3.0.0 || ^4.0.0"
+    "webpack": "^4.41.5"
   },
   "config": {
     "commitizen": {
       "path": "./node_modules/cz-conventional-changelog"
     }
+  },
+  "engines": {
+    "node": ">=8.9.4"
   }
 }