Don't mark required fields as invalid by default

I'm also not quite happy with this huge script, but the first tinier solution given in the issue on MDL totally disable the invalid functionality of MDL which we don't want:

This is how it looks like if you come to a fresh form:

When you enter a title:

When you entered a title and clicked the button:

When you click the button without entering anything:

References:

• https://github.com/google/material-design-lite/issues/1502
• https://gist.github.com/roshangautam/caefd856f9eb9e26033c0f71eebca837