Feature: use_internal_docker_network

[jrbeilke]

Yet another PR to add use_internal_docker_network feature based on @amalucelli's work in #304 as well as @AaronKalair's work in #283

Modified the container_ip method to fetch the container's .IPAddress from .NetworkSettings.Networks using docker inspect as recommended by @rs017991 and https://docs.docker.com/engine/reference/commandline/inspect/#examples

This resolves #215

[codecov-io]

Codecov Report

Merging #313 into master will decrease coverage by 0.99%.
The diff coverage is 14.28%.

@@           Coverage Diff           @@
##           master     #313   +/-   ##
=======================================
- Coverage   33.77%   32.78%   -1%     
=======================================
  Files           2        2           
  Lines         228      241   +13     
=======================================
+ Hits           77       79    +2     
- Misses        151      162   +11

Impacted Files	Coverage Δ
lib/kitchen/driver/docker.rb	31.46% <14.28%> (-0.96%)	⬇️

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[tas50]

This same functionality has been merged to master and I'll be shipping it ASAP