Optional Mount Parameters (#123)

* adding optional parameters

* updating bodyText mount prop to default

* updating snapshot for new props

* adding parent element for mounting

* adding null default for parentElement

* adding dist to gitignore

* adding test case for mounting to element

* adding div to document in test

* unmount after test

* updating test to pass

* updating eslint to handle certain rules as warning and fix others

package.json

@@ -8,7 +8,8 @@
     "start": "webpack-dev-server",
     "test": "jest",
     "test-update-snapshots": "jest --updateSnapshot",
-    "deploy": "npm run build && gh-pages -d dist"
+    "deploy": "npm run build && gh-pages -d dist",
+    "lint": "./node_modules/.bin/eslint ."
   },
   "babel": {
     "presets": [