refactor: minimum require webpack version is 4

BREAKING CHANGE: minimum require `webpack` version is `4`

Author: alexander-akait

.travis.yml

@@ -7,20 +7,17 @@ matrix:
   fast_finish: true
   include:
     - os: linux
-      node_js: "7"
-      env: WEBPACK_VERSION="2.2.0" JOB_PART=lint
+      node_js: "10"
+      env: WEBPACK_VERSION="4.15.0" JOB_PART=lint
     - os: linux
-      node_js: "6"
-      env: WEBPACK_VERSION="2.2.0" JOB_PART=test
-    - os: linux
-      node_js: "4.3"
-      env: WEBPACK_VERSION="2.2.0" JOB_PART=test
+      node_js: "10"
+      env: WEBPACK_VERSION="4.15.0" JOB_PART=test
     - os: linux
-      node_js: "7"
-      env: WEBPACK_VERSION="2.2.0" JOB_PART=test
+      node_js: "8"
+      env: WEBPACK_VERSION="4.15.0" JOB_PART=test
     - os: linux
-      node_js: "4.3"
-      env: WEBPACK_VERSION="1.14.0" JOB_PART=test
+      node_js: "6"
+      env: WEBPACK_VERSION="4.15.0" JOB_PART=test
 before_install:
   - nvm --version
   - node --version

lib/loader.js

@@ -9,7 +9,6 @@ var compileExports = require("./compile-exports");
 
 
 module.exports = function(content, map) {
-	if(this.cacheable) this.cacheable();
 	var callback = this.async();
 	var query = loaderUtils.getOptions(this) || {};
 	var moduleMode = query.modules;

lib/localsLoader.js

@@ -9,7 +9,6 @@ var compileExports = require("./compile-exports");
 
 
 module.exports = function(content) {
-	if(this.cacheable) this.cacheable();
 	var callback = this.async();
 	var query = loaderUtils.getOptions(this) || {};
 	var moduleMode = query.modules;

package.json

@@ -34,6 +34,9 @@
     "should": "^11.1.2",
     "standard-version": "^4.0.0"
   },
+  "peerDependencies": {
+    "webpack": "^4.0.0"
+  },
   "scripts": {
     "lint": "eslint lib test",
     "test": "mocha",