fix(package): update truffle to version 5.0.26

Closes #9

Author: greenkeeper[bot]

package.json

@@ -7,7 +7,7 @@
   },
   "dependencies": {
     "ganache-cli": "6.4.1",
-    "truffle": "5.0.11",
+    "truffle": "5.0.26",
     "web3": "1.0.0-beta.52"
   },
   "devDependencies": {