v6.51.1. Bugfix.

- v6.51.1 August 29, 2013
	- Fixed `docpad upgrade`
v6.51.2. Bugfix. Improvement.

- v6.51.2 August 29, 2013
	- Fixed certain pugin tests that require skeleton initialisation
(regression from v6.52.0)
	- When using `--global` flag we won't kill the global instance when
starting a skeleton