* Use "lib" in tsconfigs instead of "target".
Only add "dom" to libraries that need it. This is determined by a script, so many libraries that have "dom" maybe should not.
* Update new-package and readme
* Add back "target" where necessary
* For ReactDOM.render, make element parameter nullable to match React API and match Typescript 2.0 definition for Document.getElementById
* one more test
this allows getting the actual html element type from events.
Example:
```ts
render() {
return <input onChange={e => console.log(e.target.value)}/>
}
```
Previously you would have to cast the target manually:
```ts
render() {
return <input onChange={e => console.log((e.target as
HTMLInputElement).value)}/>
}
```
