bring the meta-viewport remove inline with other processors

dont crash if there is no viewport meta tag
adding a test for MetaViewportRemover edge case (no meta viewport tag)
Merge pull request #99 from bitzesty/fix-meta-viewport

MetaViewportRemover updates
This includes #99
Fixing the MetaViewportRemover
Merge pull request #100 from bitzesty/bump-version-to-5.0.1

Bump slimmer