Fix broken test (should return to the home page)

Nodejs.org removed the a tag from the logo. Changing the test to click on the first li element in the #nav container to load the homepage.

BEFORE CHANGE:
====================================================
  functional-tests (chrome)
    ✓ should get home page (3607ms)
    ✓ should go to the doc page (0) (2701ms)
    1) should return to the home page(0)
    2) should go to the doc page (1)
    3) should return to the home page(1)


  2 passing (38s)
  3 failing


AFTER CHANGE:
====================================================
  functional-tests (chrome)
    ✓ should get home page (2611ms)
    ✓ should go to the doc page (0) (2622ms)
    ✓ should return to the home page(0) (2791ms)
    ✓ should go to the doc page (1) (2438ms)
    ✓ should return to the home page(1) (2513ms)


  5 passing (20s)


Done, without errors.