Change behavior for placeholder attribute

[kasparsklavins]

From README.md:

If the attribute placeholder of attr is provided [...] It will be extracted as the default option.

According to html5 spec[0], placeholders are meant as hints for the input, and may contain a non-valid value

The placeholder attribute represents a short hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format

I propose removing the feature of using placeholder attribute for a default value.

[0] https://www.w3.org/TR/2011/WD-html5-20110405/common-input-element-attributes.html#the-placeholder-attribute

[nacmartin]

Uhm, yes, I think that this is right. Pass it as an extra attribute out of the specification would be better so the client can use it or not.

[kasparsklavins]

I can do a PR for this.
Is there any contributing policy?

[nacmartin]

Oh, thanks! Not really. It would be nice to add a test, though :)