Added CI_SERVER* environment variables to build process.

Better encode

The environment variable CI_SERVER can be used by the build process to
switch some specific CI configuration, like this for example:
```ruby
require 'rspec/retry'
RSpec.configure do |config|
  config.default_retry_count = 3 if ENV['CI_SERVER']
end
```
The CI_SERVER_* variables were added for completeness.

Bringing CI_BUILD_REF environment variable into master

Added Rails Environment Relative URL

CI skip with [ci skip] tag. Moved to master

update to rails 3.2.12

Moved the GitlabCi::Encode.encode! method call closer to the file read.
This keeps the boundary between "external file source with crazy
encoding -> internal rails code all in utf-8" well defined.
Additionally the build output file is opened in binary mode to prevent
encoding exceptions while reading it. It will be converted to utf-8 by
GitlabCi::Encode.encode!

Conflicts:
	app/models/build.rb

upgrade to rails 3.2.11 to avoid the recent CVE annoucements

Postgres support

Fixup cd command order