Chapter 5, Http service description of Futures corrected

Fixing prose in Chapter 5 subsection "Introducing the Http service"
since:
- the description of the behavior of `then()` was not quite right;
- described error handling in terms of `catchError()` so as to match
the updated tutorial code.
Added and updated the exercises section of Chapter 5

Added two new simpler exercises and tweaked the original one.
Fixing obvious typo (word inversion) in component class name (Ch.6)
Merge pull request #10 from chalin/patch-11-chap-05-http-svc-desc-fixed

Chapter 5, Http service description of Futures corrected
Merge pull request #11 from chalin/patch-13-new-exercises-for-Chap-05

Added and updated the exercises section of Chapter 5
Merge pull request #12 from chalin/patch-14-chap-06-typo-in-class-name

Fixing obvious typo (word inversion) in component class name (Ch.6)
Use a CDN for bootstrap & fontawesome
Merge pull request #13 from vicb/cdn

Use a CDN for bootstrap & fontawesome
Fix issue #6 (pretty printing and footer nav). Fix the favicon and homepage banner missing images as well.
Fix tutorial table of contents at tutorial/index.html
Fix up tutorial pages.
Favicon fix, slight tutorial tweak.
Fixing example and using new routing in angulardart HEAD