Avoid matching occurences of "Contact" outside heading (Ch. 5.6, ex. 1)
Visit root path in home page specs only, not all static page specs

I must have messed this up earlier: I now have the specs visiting '/'
all the time, even if they are really testing some other page.  For
other pages, it's an extra page load.

Only visit '/' when that's what we want to test.
Use shared example group for static pages (Ch. 5.6, ex. 2)
Test layout links using the title of the target page (Ch 5.6, ex. 3)
Add unit-level spec coverage for full_title helper (Ch 5.6, ex. 4)