Merge #16: Fix YAML regression in 1.9

Squashed commit of the following:

commit a26b99c64e2da4115ea47606ae8b66f0b008b002
Author: Whyme Lyu <callme5long@gmail.com>
Date:   Tue Mar 26 23:03:50 2013 +0800

    Ensure Syck is used.

    In the long run we'd better drop Syck in favor of Psych

commit a99a2b244063c2088d91688f667ee68f05f24df0
Author: Whyme Lyu <callme5long@gmail.com>
Date:   Tue Mar 26 23:03:25 2013 +0800

    A regression test for YAMLing in 1.9