Supress potential E_NOTICES about integer overflows due to unusually high/low scores.

Fixes https://github.com/elasticsearch/elasticsearch-php/issues/145

This is solved by turning of `E_NOTICE`s momentarily within the method call. The `error_reporting` value is reverted back before exiting the method call.
Perhaps add a `@todo` here so we remember to deprecate the E_NOTICE business at 2.0?