Patch for Numeric PartitionKeys

[M-Chris]

Currently a int/float/etc. value for a partition key fails without good cause..

Line 520 of CosmosDb.php should read like:

$headers['x-ms-documentdb-partitionkey'] = (is_string($partitionKey) ? '["'.$partitionKey.'"]' : '['.$partitionKey.']');

cheers