Rackspace - Switch to CoreOS for standard cluster

The Rackspace setup for Kubernetes now leverages CoreOS instead of Ubuntu. We've dropped Salt completely for our cluster.
Add Rackspace to build/release.sh

Updates to the build/release.sh scripts to upload build binaries to
Cloud Files.
remove hardcoded cloudfiles path and fix PORTAL_NET
Migrate Rackspace upload scripts to util.sh

The functions to upload built k8s tars to Cloud Files were incorrectly
placed in build/common.sh. These have been migrated to
cluster/rackspace/util.sh
Remove extra newline and update comments in util.sh
Replace custom proxy with httputil.ReverseProxy for kubecfg/kubectl.

Fixes #1149 - kubecfg proxy "411 Length Required" error on POST/PUT.
build: switch to golang:1.3 and build go for KUBE_CROSSPLATFORMS
build: add kube-build:cross base
build: fix golang pull message
Add create/delete minion to client interface.
Script to do an "official" release push to GCS.
Merge pull request #1832 from doublerr/rackspace_switch_to_coreos

Rackspace - Switch to CoreOS for standard cluster
Increase memory limit of frontend-controller in our guestbook example.
Merge pull request #1953 from jbeda/official-release

Script to do an "official" release push to GCS.
Add client time to events
Merge pull request #1950 from ddysher/client-minion-interface

Add create/delete minion to client interface.
Merge pull request #1955 from lavalamp/fix3

Add client time to events
Rename ID -> Name
Replace use of "id" in strings with "name"
Merge pull request #1962 from dchen1107/fix

Increase memory limit of frontend-controller in our guestbook example.