Add attach command to weave.
attach command that accepts and existing container id and runs configure_container_networking using it
Merge branch 'add-attach' of https://github.com/adieu/weave into 67_attach
Merge branch 'master' of https://github.com/binocarlos/weave into 67_attach

Conflicts:
	weaver/weave
Merge remote-tracking branch 'upstream/master' into 67_attach
Add detach command
Untabify
Described attach and detach commands
Redesigned attach/detach
Updated instructions for attach and detach
Improved test for blank string
Make attach and detach idempotent
Merge branch '67_attach' of https://github.com/bboreham/weave into bboreham-67_attach
Merge branch '67_attach' of https://github.com/bboreham/weave into bboreham-67_attach
tweak & move docs for 'attach' and 'detach'
Capture error output from ip command and check if error was caused by container dying
Merge remote-tracking branch 'upstream/bboreham-67_attach' into 67_attach
Merge branch 'master' into bboreham-67_attach
Refactor common code in attach/detach
Rename 'configure_container_networking' to 'attach'