fix: move babel-core to peerDependencies & devDependencies (#20)

BREAKING CHANGE: You'll have to install `babel-core` yourself now.

package.json

@@ -21,21 +21,24 @@
   "author": "Kent C. Dodds <kent@doddsfamily.us> (http://kentcdodds.com/)",
   "license": "MIT",
   "dependencies": {
-    "babel-core": "^6.25.0",
     "common-tags": "^1.4.0",
     "invariant": "^2.2.2",
     "lodash.merge": "^4.6.0",
     "path-exists": "^3.0.0",
     "strip-indent": "^2.0.0"
   },
   "devDependencies": {
+    "babel-core": "^6.25.0",
     "babel-plugin-syntax-trailing-function-commas": "^6.22.0",
     "babel-plugin-transform-async-generator-functions": "^6.24.1",
     "babel-plugin-transform-async-to-generator": "^6.24.1",
     "babel-plugin-transform-object-rest-spread": "^6.26.0",
     "babel-preset-env": "^1.5.2",
     "kcd-scripts": "^0.16.3"
   },
+  "peerDependencies": {
+    "babel-core": "^6.0.0 || ^7.0.0-alpha || ^7.0.0-beta || ^7.0.0"
+  },
   "eslintConfig": {
     "extends": "./node_modules/kcd-scripts/eslint.js",
     "rules": {