Lodash 4.17.0 _.pick breaks when there are dots in keys

With lodash 4.16.6:

```
> _.pick({'foo.txt': 'foo', 'bar.txt': 'bar', 'baz.txt': 'baz'}, ['foo.txt', 'baz.txt'])
{ 'foo.txt': 'foo', 'baz.txt': 'baz' }
```

With lodash 4.17.0:

```
> _.pick({'foo.txt': 'foo', 'bar.txt': 'bar', 'baz.txt': 'baz'}, ['foo.txt', 'baz.txt'])
{ foo: { txt: 'foo' }, baz: { txt: 'baz' } }
```