chore(package): update simple-git to version 2.5.0

Closes #497

Author: greenkeeper[bot]

package.json

@@ -46,7 +46,7 @@
     "mkdirp": "^0.5.1",
     "mocha": "^5.0.0",
     "semantic-release": "^15.5.1",
-    "simple-git": "^1.45.0",
+    "simple-git": "^2.5.0",
     "sinon": "6.0.1",
     "sinon-chai": "^3.2.0",
     "validate-commit-msg": "^2.6.1"