Hotfix: EmbedOne DiscriminatorMap

Fixes a bug that prevented:

/**
 * @ODM\EmbedOne(
 *      discriminatorField="type",
 *      discriminatorMap={
 *         "RecordLabel"    = "Zoop\Shard\Test\ODMCore\TestAsset\Document\RecordLabel",
 *         "Artist"         = "Zoop\Shard\Test\ODMCore\TestAsset\Document\Artist"
 *      }
 * )
 */
protected $license;

ZF2 v2.3

Updates shard dependencies to ZF2 v 2.3.

Hotfix: Nested Abstract Embeds

Fixes:

• Unserialize Nested Abstract Embeds #56
• EmbedMany with a discriminatorMap #55