valid-describe blows up on template strings (backticks)

I have a pattern where I prefer backticks for test/describe names (makes apostrophes easier to juggle, and helps call out strings that are user-visible vs those that aren't)

However, `valid-describe` blows up on 'em:

```js
describe(`foo`, () => { … }); // Error: First argument must be name
describe('foo', () => { … }); // OK
```