Fix for loading assets with no file extension.

Closes #98.
Warn when loading a file with no extension and no explicit type.
Merge branch 'master' into haxe3

* master:
  Warn when loading a file with no extension and no explicit type.
  Fix for loading assets with no file extension.
Goodbye _internal_, hello @:allow.

http://haxe.org/manual/acl. This alone is reason to upgrade to Haxe 3.