Remove git hooks support

The `ghooks` package doesn't work well with GUI git tools.  They're
aware of that and working on the issue (see
ghooks-org/ghooks#40), but for now I'm
removing them from this PR.

I'll watch that issue and re-consider once they've resolved it.

Even if you opt out of the hooks, they still have to run just enough to
know to opt out.

.gitignore

@@ -1,5 +1,3 @@
 node_modules/
 public/
 .tmp/
-.opt-in
-.opt-out

package.json

@@ -16,13 +16,6 @@
     "test:watch": "npm run test -- --watch --reporter min",
     "validate": "npm-run-all --parallel test lint"
   },
-  "config": {
-    "ghooks": {
-      "pre-push": "opt --out pre-push --exec 'npm run validate'",
-      "post-checkout": "opt --out post-checkout --exec 'npm install'",
-      "post-merge": "opt --out post-merge --exec 'npm install'"
-    }
-  },
   "repository": {
     "type": "git",
     "url": "git+https://github.com/CodingZeal/react-boilerplate.git"
@@ -96,10 +89,6 @@
     "webpack": "^1.13.1",
     "webpack-dev-server": "1.14.0"
   },
-  "devDependencies": {
-    "ghooks": "^1.2.4",
-    "opt-cli": "^1.4.2"
-  },
   "babel": {
     "presets": [
       "react",