Write logger output to stderr to conform to convention

Writing log to stdout causes issues when piping.
Update Nokogiri version
Check if security group is nil, fixes #2507
Merge pull request #2569 from gaurish/security_group_check

Check if security group is nil, fixes #2507
Fix version
Undo last nokogiri version setting
Merge pull request #2575 from skorth/master

Update Nokogiri version
Merge pull request #2390 from revapost/master

Write logger output to stderr to conform to convention