Removed count function. Fixes ErickTamayo#80 (ErickTamayo#84)

Since php 7.2, count a number will generate a warning. Because
$results['hits']['total'] is a number we can just compare it to zero.

`if ($results['hits']['total'] === 0)`

Fixed error in readme config example (ErickTamayo#83)

Enable Laravel5.5 package Auto-Discovery (ErickTamayo#81)

Execute the callback that can be passed to the Builder in performSear…

…ch (ErickTamayo#56)

Context: laravel/scout#111

Implementation analogical to the official AlgoliaEngine implementation: https://github.com/laravel/scout/blob/v3.0.3/src/Engines/AlgoliaEngine.php#L112-L119

Support for "WHERE IN" searches if array is passed to `where` (ErickT…

…amayo#55)

Right now passing an array results in: "illegal_state_exception: Can't get text on a START_ARRAY"
Solution based on http://stackoverflow.com/a/40737488/7362396

chain `values` method in `map` function (ErickTamayo#66)

In 
```php
    collect($results['hits']['hits'])->map(function ($hit) use ($model, $models) {
            return isset($models[$hit['_id']]) ? $models[$hit['_id']] : null;
        })->filter();
```
would generate some holds which would cause `paginate` results objects rather than list.

Update ElasticsearchProvider.php (ErickTamayo#54)

use `app` instead of `resolve` to make lumen 5.4 compatible.

`app` and `resolve` are identical since 5.4, see https://github.com/laravel/framework/blob/5.4/src/Illuminate/Foundation/helpers.php#L690

v3.0.2

bumping to php 5.6.6 (Earliest version that can support php elasticsearch) (ErickTamayo#48)
`within` now is being taken into account when specified ErickTamayo#31
Now if the record is not found on the db will not throw undefined offset ErickTamayo#36
Implemented orderBy ErickTamayo#46