Nested NamespaceCachePools should trim the seperator #77

Nested NamespaceCachePools have multiple HIERARCHY_SEPARATORs concatted together.

Example:

$cachePoolApp=new \Cache\Namespaced\NamespacedCachePool($cachePool, 'app-name');
$cachePoolVersion=new \Cache\Namespaced\NamespacedCachePool($cachePoolApp, 'code-version');
$cachePoolInstance=new \Cache\Namespaced\NamespacedCachePool($cachePoolVersion, 'instance-id');

Saving to key test will generate the key |app-name||code-version||instance-id|test.
I expected app-name|code-version|instance-id|test to be the key.

Are the multiple seperators planned behaviour?

(Is the prefixed seperator |app-name necessary? It seems a bit odd.)