Revert "Use old 'syck' module for YAML parsing"

This reverts commit d8f17699fc830663221c429b9ec28bed689f6da8.
Add tool to convert YAML objects from syck to psych.
Use supmua.org for YAML_DOMAIN
Use different backup name as .bak already is used in lib/sup.rb and +x
add sup-psych-ify--- to SUP_EXECUTABLES
Only support Ruby 1.9.2+, dropping 1.8
Support loading legacy YAML for now.
Remove redundant self.instance_eval
Remove dead & deprecated code
Now sources.yaml migration is just load & save
Mention psych-ify in gemspec.post_install_message
Set yamler explicitly for 1.9.2
Merge pull request #75 from 5long/migrate-to-psych

Migrate to Psych