Update links to download page

Downloads for go have moved from code.google.com to golang.org/dl
added an unknown styling file (no idea what it is for)
Merge pull request #8 from tbroyer/patch-1

Update links to download page
naked return example should be naked
Merge pull request #9 from reedobrien/master

naked return example should be naked
Corrected typo
Code snippet does not reflect the playground link
Merge pull request #10 from sindice/master

Corrected typo
Added one tip and a section on importing packages to tricks_and_tips.md.
Merge pull request #11 from Xercoy/master

Added one tip and a section on importing packages to tricks_and_tips.md.
minor improvements in copy of section 'Skills' of Chapter 1: 'Intro'
Merge pull request #12 from tapank/master

minor improvements in copy of section 'Skills' of Chapter 1: 'Intro'
removed an incomplete sentence
removed an incomplete sentence in section '2.2 Constants' chapter 2 'The Basics'
Merge branch 'master' of github.com:tapank/book
changed broken sec to cha x-refs in types.md

* atom editor added some return chars
Merge pull request #14 from nickmerwin/master

changed broken sec to cha x-refs in types.md
Merge pull request #13 from tapank/master

removed an incomplete sentence in section 'Constants' chapter 2 'The Basics'