[Patch] duplicate assets on windows fixes #135

Quick, and "dirty" trick to normalize assets paths. I couldn't use `realpath()` for this purpose, so decided to replace `\`  with unix directory separator `/`.

Also during this time one thing happened. My changes from PR #140 were somehow reverted.. I've put them back, because without it occurred some problems with assets order.

Unit test for that would be useful, but for now I don't have enough time to write it :(