Revert "switched to thin for stress test purpose only"

This reverts commit 441cc5d62312150fe136540ee989a379fedbd094.
Revert "switched to webrick for stress test purpose"

This reverts commit 527343afd580d6bee3e8407a347f34151e719552.
Revert "switched to unicorn for stress tests purpose only"

This reverts commit 73728529d778fc47b68795faed7bbc84c3945763.