Bump simple-git and lint-staged

Removes [simple-git](https://github.com/steveukx/git-js/tree/HEAD/simple-git). It's no longer used after updating ancestor dependency [lint-staged](https://github.com/okonet/lint-staged). These dependencies need to be updated together.


Removes `simple-git`

Updates `lint-staged` from 8.1.0 to 13.1.0
- [Release notes](https://github.com/okonet/lint-staged/releases)
- [Commits](https://github.com/okonet/lint-staged/compare/v8.1.0...v13.1.0)

---
updated-dependencies:
- dependency-name: simple-git
  dependency-type: indirect
- dependency-name: lint-staged
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

README.md

@@ -1,6 +1,6 @@
 # Pjax
 
-[![Build Status](https://img.shields.io/travis/MoOx/pjax.svg)](https://travis-ci.org/MoOx/pjax)
+[![Build Status](https://img.shields.io/travis/MoOx/pjax.svg)](https://travis-ci.org/MoOx/pjax).
 
 > Easily enable fast AJAX navigation on any website (using pushState() + XHR)
 

package.json

@@ -33,7 +33,7 @@
     "husky": "^1.2.0",
     "jsdom": "^11.5.1",
     "jsdom-global": "^3.0.2",
-    "lint-staged": "^8.1.0",
+    "lint-staged": "^13.1.0",
     "npmpub": "^3.1.0",
     "nyc": "^11.4.1",
     "opn-cli": "^3.1.0",