Upgrade rollup to fix failure to emit declarations

Author: marijnh

package.json

@@ -36,7 +36,7 @@
     "tslib": "1.10.0"
   },
   "peerDependencies": {
-    "rollup": ">=1.26.0",
+    "rollup": ">=1.26.3",
     "typescript": ">=2.4.0"
   },
   "devDependencies": {
@@ -54,7 +54,7 @@
     "lodash": "4.17.15",
     "object-hash": "1.3.1",
     "rimraf": "3.0.0",
-    "rollup": "^1.26.0 ",
+    "rollup": "^1.26.3 ",
     "rollup-plugin-commonjs": "10.1.0",
     "rollup-plugin-node-resolve": "5.2.0",
     "rollup-plugin-re": "1.0.7",