Heading classNames mess

[DimitarChristoff]

Using <Heading> produces a <h1 class="title subtitle"> - the assertion is to check if heading is set and if not, adds class subtitle always.

https://github.com/couds/react-bulma-components/blob/master/src/components/heading/heading.js#L45-L46

adding heading={true} removes subtitle but also removes class title.

aim to me is to get <h1 class="title is-1"> by default - otherwise, if you have different stylings in bulma for title and subtitle, the subtitle colour is applied to your heading.