Careers page needs a slight revamp

[prokoudine]

The Careers page has several issues.

1. The menu item says 'Careers', but the page title says 'Jobs'. I submitted Rename Jobs to Careers in the title for consistency's sake #48 to fix that.
2. Unlike other pages, this page doesn't render a title in the top middle. It should.
3. When there are no positions available, it will grab content from the About page which is weird. Let's not do that and just display "There are no current openings." instead.

[patdavid]

Ah, interesting.

I've updated the page to include the title in the top middle the same as the other pages.

In looking at rendering the "about" information it appears that this is a function of the "Greenhouse" job board and not something we control on our end. If we want that information to change it looks like it would have to happen there. (Don't know who controls that page - @sliptonic?)