Added a configuration variable: keep_files (default: ['.git']), based on this pull request: https://github.com/mojombo/jekyll/pull/556
removed puts
use Array.join instead of Array.inject, add .svn to defaults
Changes based on @mojombo's feedback
merge lastest from mojombo/jekyll master
Merge pull request #685 from edeustace/keep_files_feature

Keep files feature