Navbar minor issues since PR #77

[leducvin]

Hello, quite the CSS novice here, but I believe PR #77 slightly broke several themes:
Flatly, Darkly, and a few others. No apparent issue in the default theme, however.

They still look good, but have minor issues with what used to be the navbar inside hero at the top of the page.

One can see rounded corners around the navbar at the top, i.e. border-radius is not 0.

Also, in some themes such as Flatly, the very first header h1 (title of the site) is of primary color or very close, so contrast is very poor.
I suppose there should be some selector .navbar.is-primary .title specifying the proper text color for the theme?