Header component updated to our basic structure with nav element / logo items left to #12. Header will display page headline if "headline" prop is passed; otherwise will hide
Footer: new component created and completed. A few todos included to not hardcode info, etc... Awaiting #27 and #17 for these updates
Layout: restructured to call Header and Footer components properly.
Note: Merge PR 26 first!
Updated layout component as follows: