change order of transformers, put function below the guard

[alextes90]

Have faced with the error, when use keepOnlyAttributeSizes. The error was attrStr.split is not a function. After investigation has found that the error coms from transformers => removeInlineSizes.js => parseAttrs => _attr => parseAtr. The reason was that transformer removeUnusedCSS remove classes and leave class attribute as is. And than while parsing not the string was the argument but the boolean, wich caused the error.
So I change the order of transformers so after the removeInlineCSS will invoke removeAttributes wich will remove single class attribute.
Also while investigating has found that there is sense to move parsing below the guard in removeInlineSizes.js to prevent some unnecessary operations.

[cossssmin]

Hey, thanks for this! I'll need to run some more checks to make sure it doesn't break anything else (even though tests are passing right now) 👍