doc/contribute: golang-dev -> golang-codereviews

https://code.google.com/p/go/source/diff?spec=svnb3caf13d930b2804458315c2c9371443e310c9ef&old=3293eec97f4c858334f7ddb0e0464b1dcf0bc51c&r=b3caf13d930b2804458315c2c9371443e310c9ef&format=unidiff&path=%2Fdoc%2Fcontribute.html
2014: Year of the Gopher.

https://code.google.com/p/go/source/diff?path=/doc/contribute.html&format=unidiff&r=c344ec9f431817e5bf19d161b38ba2eaff9fc7dc
git: add .DS_Store to gitignore