Provide field config defaults for fuzzy and boost properties

[andymerskin]

Currently, Spotr's field configuration requires you to pass an object with fuzzy and boost and doesn't provide defaults if you want to get up and going with Spotr immediately.

Ideally, one could configure Spotr with an array of fields, like so:

const search = new Spotr({
  collection: bigArrayOBooks,
  fields: ['title', 'genre']
})

And then queries could be scored against those fields without extra configuration.

search.query('The Great Gatsby')