Fixes issues with mounting subdirectories of /mnt in container.

Tested with
mkdir /mnt/data
docker run -v /mnt/data:/mnt/data  -t ubuntu:12.10 touch /mnt/data/bar

Expected /mnt/data/bar on host.
check return value of syscall.Chdir when changing working directory
make copy paste user friendly

copying only the first line killed my sources.list file
c&p improvement for 13.04

first line killed sources list
clean split between errors and output. JSON output always valid
Fix #2302
Place 'top' subcommand's help in proper order.
Merge pull request #2303 from metalivedev/2302-fixintro

Fix #2302
Fix github link in docs
Clean up level 3 headers.
Set commentstring in Vim syntax plugin

By setting the commentstring, you support commenting with plugins like tComment.
Now Vim won't default to incorrect `/* */` comments.
Merge pull request #2307 from gurjeet/sorted_commands_in_help

Place 'top' subcommand's help in proper order.
Merge pull request #2326 from justinforce/commentstring

Set commentstring in Vim syntax plugin
Merge pull request #2198 from hamo/hamo/chdir_error

check return value of syscall.Chdir when changing working directory
Merge pull request #2318 from Tranquility/master

Fix github link in docs
Merge pull request #2150 from pnasrat/fix-mnt-subdir-volumes

Fixes issues with mounting subdirectories of /mnt in container.
Merge pull request #2261 from edmund-wagner/master

make copy paste user friendly
registry: fix content-type for PushImageJSONIndex
Merge pull request #2338 from proppy/patch-1

Registry: Fix content-type for PushImageJSONIndex
fix race condition in docker build with verbose + cleanup hostIntegration debug