Add messages about processing global and pattern specific data

Make sure $rendered variable is set

Merge pull request #26 from gambry/bugfix/23-php-notice-undefined-index

Avoid "Undefined index" PHP Notice

Fix NodeVisitor variable reference

Update license identifier

Update README

Temporarily restrict Twig version

Merge branch 'dev'

Merge branch 'dev'

Merge pull request #3 from EvanLovely/patch-1

Bumping requirements up to 2.0.0 release