[BUGFIX] Change check on Asset "path" to cover 4.5 misbehavior

Instead of using isset() which always returns TRUE for the ArrayAccess used in 4.5's Fluid, the check needs to be extended.

Replaces: #150
[BUGFIX] Name generation for assets buggy on 4.5

This fixes some issues with incomplete (always-TRUE) checks on 4.5 and uses serialize() to avoid collisions on ArrayAccess sameness which would often occur on 4.5.

Replaces: #149
Merge pull request #158 from NamelessCoder/pathcheck

[BUGFIX] Change check on Asset "path" to cover 4.5 misbehavior
Merge pull request #159 from NamelessCoder/assetnames

[BUGFIX] Name generation for assets buggy on 4.5