[Container-tools] Atomic App 0.5.1 Release!

[Charlie Drage]

This is a minor release of Atomic App where we refactor, fix code bugs
as well as deprecate an old feature. Due to the numerous issues of
locking as well as the deprectation of the `lockfile` library we have
removed the locking mechanism from Atomic App.

The main features of this release are:

  - The deprecation of locking
  - `atomicapp init` code and UI clean-up
  - Documentation updates
  - inContainer() function bug fix for Docker 1.10+

```
Charlie Drage <charlie at charliedrage.com>:
      Add Marathon to index
      Update README.md with correct installation instructions.
      Remove dockerenv and dockerinit check
      Remove locking from Atomic App

Dusty Mabe <dusty at dustymabe.com>:
      init: remove unnecessary message to the user
      init: remove number of return variables from NuleculeManager.init()
      init: add logic to properly cleanup tmp dir
      init: break a few long lines into shorter ones

Shubham Minglani <shubham at linux.com>:
      fix typo

Suraj Deshmukh <surajssd009005 at gmail.com>:
      Moved a constant from openshift.py to constants.py
      Abstracted the way we get absolute path
```

Many thanks to those whom contributed to this release!

-- 

Charlie Drage
Red Hat - OSAS Team / Project Atomic
4096R / 0x9B3B446C
http://pgp.mit.edu/pks/lookup?op=get&search=0x622CDF119B3B446C