fixed #910. print user name to docker info output
Added index address into APIInfo.
fixing #910
Forbid certain paths within docker build ADD
Merge pull request #1450 from dotcloud/add-sandbox

- Builder: Forbid certain paths within docker build ADD
Merge pull request #1093 from monnand/910-login-info

* Runtime: fixed #910. print user name to docker info output
Add warning when net.ipv4.ip_forwarding = 0

Added warnings to api.go, container.go, commands.go, and runtime.go
Also updated APIInfo to return whether IPv4Forwarding is enabled
Add Colin Rice to AUTHORS file
Fix reversed IPv4Forwarding check in api.go