remove DEPRECATION WARNING for after_filter in Rails5
remove DEPRECATION WARNING for after_filter in Rails5

```
DEPRECATION WARNING: after_filter is deprecated and will be removed in
Rails 5.1. Use after_action instead. (called from block in included at
/home/travis/build/mileszs/wicked_pdf/lib/wicked_pdf/pdf_helper.rb:12)
```

bonekost/wicked_pdf,mileszs/wicked_pdf