Security warnings in LXC configuration

*Builder: warn pre-1.3 clients that they need to upgrade. This breaks semver, but our API should still be in 0.X versioning, in which case semver allows breaking changes.

* Builder: correct the behavior of ADD when copying directories.

- Runtime: Forbid parralel push/pull for a single image/repo. Fixes #311

* Documentation: replace `ifconfig` in docs with `iproute`

* Documentation: use https repo url to clone for dev setup instructions

* Build: Stabilize ADD behavior

the git clone line in the dev setup instructions does not work as is, unless the user has write access

* Client: HumanReadable ProgressBar sizes in pull

Fix Mac OS X installation instructions URL

* Builder: fixed the behavior of ADD to be (mostly) reverse-compatible, predictable and well-documented.

Vagrantfile: Add support for VMWare Fusion provider 

* Runtime: Remove bsdtar dependency

- Runtime: Fix race condition within Run command when attaching.

* Builder: nicer output for 'docker build'

Add image lookup to history command

- Documentation: fix missing command in irc bouncer example

Fixed #923 by replacing the usage of 'ifconfig' with 'ip a' where appropriate and added a note to use 'ip a' instead of 'ifconfig' for a screencast transscript.

Fixes on documentation. LGTM