Add real model name to Eloquent integration

[eggnaube]

Add real model name to Eloquent integration, instead of the base class name.

// protected function performInsert(Builder $query)
opencensus_trace_method(Model::class, 'performInsert', function ($model, $query) {
	return [
    	'name' => get_class($model) . '::performInsert',
        'attributes' => [
        	'query' => $query->toBase()->toSql()
        ],
        'kind' => Span::KIND_CLIENT
    ];
});

If you wish, i could open a PR with the changes, including tests.