fix(package): update simple-git to version 2.1.0

Closes #69

Author: greenkeeper[bot]

package.json

@@ -53,7 +53,7 @@
     "lodash.groupby": "^4.6.0",
     "pify": "^4.0.1",
     "semver": "^7.1.1",
-    "simple-git": "^1.131.0",
+    "simple-git": "^2.1.0",
     "trace-and-clarify-if-possible": "^1.0.5"
   },
   "devDependencies": {