Update language server to v4

composer.json

@@ -2,6 +2,29 @@
     "minimum-stability": "dev",
     "prefer-stable": true,
     "require": {
-        "felixfbecker/language-server": "^3.1.0"
-    }
+        "felixfbecker/language-server": "^4.1.1"
+    },
+    "scripts": {
+        "parse-stubs": "LanguageServer\\ComposerScripts::parseStubs",
+        "post-update-cmd": "@parse-stubs",
+        "post-install-cmd": "@parse-stubs"
+    },
+    "repositories": [
+        {
+            "type": "package",
+            "package": {
+                "name": "JetBrains/phpstorm-stubs",
+                "version": "dev-master",
+                "dist": {
+                    "url": "https://github.com/JetBrains/phpstorm-stubs/archive/master.zip",
+                    "type": "zip"
+                },
+                "source": {
+                    "url": "https://github.com/JetBrains/phpstorm-stubs",
+                    "type": "git",
+                    "reference": "master"
+                }
+            }
+        }
+    ]
 }

package.json

@@ -53,6 +53,6 @@
   "dependencies": {
     "mz": "^2.4.0",
     "semver": "^5.3.0",
-    "vscode-languageclient": "^2.5.0"
+    "vscode-languageclient": "^3.0.1-alpha.14"
   }
 }