Fix YAML Regression in 1.9

After I could build a sup.gem locally, the first program I run was `sup-config`. Syck and Psych behave differently and current codebase just assumes Syck is used everywhere. Problem is, `sup-config` loads yaml(in 1.9 that's Psych) before `lib/sup.rb`, and the whole ruby process just uses Psych all the way down, producing this bug.

This patch fixed it.