Adopt version 0.0.18 of the language server (#291)

This update includes a few bug fixes as well as additional linting
checks.

Signed-off-by: Remy Suen <remy.suen@gmail.com>

package.json

@@ -639,15 +639,15 @@
     "azure-arm-containerregistry": "^1.0.0-preview",
     "azure-arm-resource": "^2.0.0-preview",
     "azure-arm-website": "^1.0.0-preview",
-    "dockerfile-language-server-nodejs": "^0.0.17",
+    "dockerfile-language-server-nodejs": "^0.0.18",
     "dockerode": "^2.5.1",
     "gradle-to-js": "^1.0.1",
     "moment": "^2.19.3",
     "opn": "^5.1.0",
     "pom-parser": "^1.1.1",
     "request-promise": "^4.2.2",
     "vscode-extension-telemetry": "^0.0.6",
-    "vscode-languageclient": "^4.0.0",
+    "vscode-languageclient": "^4.2.1",
     "glob": "7.1.2"
   }
 }