fix: update rollup to version ^0.51.0 (#260)

Author: renovate[bot]

package.json

@@ -39,7 +39,7 @@
     "postcss": "^6.0.2",
     "read-file": "^0.2.0",
     "rimraf": "^2.6.1",
-    "rollup": "^0.50.0",
+    "rollup": "^0.51.0",
     "rollup-plugin-commonjs": "^8.2.1",
     "rollup-plugin-node-resolve": "^3.0.0",
     "sorcery": "^0.10.0",

yarn.lock

@@ -3058,9 +3058,9 @@ rollup-pluginutils@^2.0.1:
     estree-walker "^0.3.0"
     micromatch "^2.3.11"
 
-rollup@^0.50.0:
-  version "0.50.0"
-  resolved "https://registry.yarnpkg.com/rollup/-/rollup-0.50.0.tgz#4c158f4e780e6cb33ff0dbfc184a52cc58cd5f3b"
+rollup@^0.51.0:
+  version "0.51.0"
+  resolved "https://registry.yarnpkg.com/rollup/-/rollup-0.51.0.tgz#bee110391dd42a48d61f31804807a80be4a085e5"
 
 rxjs@^5.4.0:
   version "5.5.0"