Makefile: rebuild node-sass to fix build error on Travis

See: https://github.com/sass/node-sass/issues/1579#issuecomment-227663782

Makefile

@@ -116,6 +116,7 @@ package-lock.json: package.json
 
 stamp-npm: $(LERNA) package.json package-lock.json src/headless/package.json
 	npm run lerna
+	npm rebuild node-sass
 	touch stamp-npm
 
 .PHONY: clean

package-lock.json

@@ -2726,34 +2726,6 @@
 				"execa": "^1.0.0",
 				"is-ci": "^2.0.0",
 				"npmlog": "^4.1.2"
-			},
-			"dependencies": {
-				"clone-deep": {
-					"version": "4.0.1",
-					"resolved": "https://registry.npmjs.org/clone-deep/-/clone-deep-4.0.1.tgz",
-					"integrity": "sha512-neHB9xuzh/wk0dIHweyAXv2aPGZIVk3pLMe+/RNzINf17fe0OG96QroktYAUm7SM1PBnzTabaLboqqxDyMU+SQ==",
-					"dev": true,
-					"requires": {
-						"is-plain-object": "^2.0.4",
-						"kind-of": "^6.0.2",
-						"shallow-clone": "^3.0.0"
-					}
-				},
-				"kind-of": {
-					"version": "6.0.3",
-					"resolved": "https://registry.npmjs.org/kind-of/-/kind-of-6.0.3.tgz",
-					"integrity": "sha512-dcS1ul+9tmeD95T+x28/ehLgd9mENa3LsvDTtzm3vyBEO7RPptvAD+t44WVXaUjTBRcrpFeFlC8WCruUR456hw==",
-					"dev": true
-				},
-				"shallow-clone": {
-					"version": "3.0.1",
-					"resolved": "https://registry.npmjs.org/shallow-clone/-/shallow-clone-3.0.1.tgz",
-					"integrity": "sha512-/6KqX+GVUdqPuPPd2LxDDxzX6CAbjJehAAOKlNpqqUpAqPM6HeL8f+o3a+JsyGjn2lv0WY8UsTgUJjU9Ok55NA==",
-					"dev": true,
-					"requires": {
-						"kind-of": "^6.0.2"
-					}
-				}
 			}
 		},
 		"@lerna/conventional-commits": {