check redhat-release first

1) Check for redhat-release must be done first because puma's initscript is lsb-compliant. To run such scripts we need redhat-lsb-core package installed which provides /etc/lsb-release too.
2) /etc/lsb-release existence is not a good way to check for debian anyway.
Application pre-loading is optional now (set puma_preload_app to false to turn it off)
Version bump
Merge pull request #34 from marshall-lee/master

check redhat-release first
check for linked_dirs var and raise with meaningful error msg
bugfix: sort array before compare
move code into puma:check task

- and remove Array monkey patch, use set instead