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.
Could you include the invalid JSON error code in this exception, so the end user knows what caused it to blow up?