Deleted references to AUFS

AUFS is no longer a dependency (both lxc-docker and lxc-docker-git are >=0.7), and the Arch kernel doesn't need to be replaced with AUFS_friendly.
Arch docs: Updated dependencies to match AUR

The AUR packages lxc-docker and lxc-docker-git have changed their dependencies.
Arch docs: Added lxc-docker-nightly AUR package, modified deps

lxc-docker-nightly installs latest build. Removed go from dependencies, as it is not needed in lxc-docker and lxc-docker-nightly. The -git package will flag go as a dependency upon installation.
Update systemd service file with suggestions from @seblu
Document setting up Vagrant-docker with the remote API
Remove incorrect SIGKILL handler.

As per POSIX signal handling SIGKILL does not work.

Fixes #2928
Return process exit code for attach

Fixes #2240
Make race condition more obvious by performing more asserts
Make CopyEscapable consistent with Copy and return `nil` in case of success instead of io.EOF
Merge pull request #2901 from dkumor/patch-1

Deleted references to AUFS in Arch docs
Merge pull request #2357 from ulyssecarion/master

Document setting up Vagrant-docker with the remote API
Merge pull request #2692 from SvenDowideit/add-specific-feedback-for-bad-ADD

Add specific feedback for ADD outside context
Closing connection after ping
Make sure the container is running before testing against it (TestAttachDetach)
Add a GetPtyMaster() method to container to retrieve the pty from an other package.

We could also have put ptyMaster public, but then we need to ignore it in json
otherwise the Marshalling fails. I think it is cleaner that way.
Make the PTY in raw mode before assert test (TestAttachDetach)
Actually test the detach (was not the case before)
Fix term.RestoreTerminal behavior
Make sure the termcaps are restored after hijack
Create helper function for tests