add sentinel font to external stylesheet for jobs, remove hardcoded font...

... family, adjust css for breaking layouts when screen resizing

Addresses https://github.com/optimizely/marketing-website/issues/534 and https://github.com/optimizely/marketing-website/issues/534.

Added the Sentinel font to be loaded from an external stylesheet.  We had this setup already for the nonprofits page.  Sentinel and Gotham were hardcoded without variables in the CSS.  I'm not sure why these fonts are mixed on this page.  Not sure if we want to leave it this way?  I removed the hardcoding and used our SASS variables for these fonts in the jobs SASS.

Refactored CSS and classes in HTML to fix the resizing issue where layout of the jobs list items was breaking.  To test, size down and back up the screen.  See that the layout for the job title and the job location do not become broken anymore.