add Mustache dependency
transform scaffold raw php templates into mustache templates

* move common code into helper method
* make taxonomy template more consistent with cpt template
* rename --label to --singular
replace {{post_type}} with {{slug}}
use {{label}} instead of {{slug}}, where appropriate
pass whole post to get_permalink() and cache the result
remove @maintainer and @subpackage tags
Merge pull request #265 from wp-cli/scaffold-mustache

Use Mustache for scaffold templates