[#77] Introduce Fig - isolated snakebite testing

Notes:
 * Fig is not integrated with setuptools, running python setup.py test
   will use Tox for testing
 * Fig still uses standard python setup.py test (including Tox) but
   inside separate/isolated OS/container
 * Requires Docker installed on your machine(!)

PR provides fig configuration for:

+-------------------- -+-------------+
|  description         |   command   |
+----------------------+-------------+
|  dirty testing image |    dirty    |
|    py2.7 and HDP     | testPy27hdp |
|    py2.7 and CDH     | testPy27cdh |
|    py2.6 and HDP     | testPy26hdp |
|    py2.6 and CDH     | testPy26cdh |
+----------------------+-------------+

So how to start:
 * fig build ( should build your current dirty image)
 * fig run testPy27hdp (to run isolated py2.7 tests on HDP)

To run all tests at the same time run:
 * fig up
Not tho this is actually requires so resources.

Details:

1. Improve setup_env

 * handle only-download, only-extract, distro-select
 * add nice flags and nice flag handler

2. Add fig to dev requirements

3. Add Dockerfile for dirty testing image

 * image used to build dirty testing images
 * based on ravwojdyla/snakebite_test:base
 * copies your local dirty code base
 * install all dev requirements from your dev requirements

4. Add fig configuration file

5. Add Dockerfile for snakebite_test:base

 * base image for dirty testing images
 * based on dockerfile/java:oracle-java7
 * downloads cdh/hdp tarballs
 * install python 2.6 and 2.7
 * install pip

6. Add script to build snakebite_test:base