Fixed undefined variable timezone in Rakefile

It made it impossible to create a new page on 2.1
Merge pull request #1026 from gkarekinian/undefined_timezone_variable

Fixed undefined variable timezone in Rakefile
Cherry-pick fail.
Fixed issue with mobile nav choosing the last option by default. Fixes #950.
Merge branch '2.1' of git://github.com/imathis/octopress into testing-2.1
Update Octopress.
Update Gemfile.lock
CoffeeScript.