[Closes #118] Update website and Travis config.

- Update all broken links: internal and external
- Update content: Hudson is Jenkins, presentations, small cleanups
- Update nanoc for 3.6.x fixes to check exit status (updates SASS too)
- Rakefile with default 'test' task for Travis (change .travis.yml)
Merge pull request #148 from richardkmichael/118-validate_links_on_travis_test

[Closes #118] Update website and Travis config.