Sleep before retrying SSH#establish_connection.

This addresses a race condition where the remote instance might be
restarting its sshd process and is therefore unavailable for a second or
two.
install driver gems with Gem::GemRunner
disable safe yaml for driver gem loading
add explaination/when can be removed
Merge pull request #416 from mcquin/gem_runner-install-driver

Gem runner install driver
Merge pull request #399 from test-kitchen/ssh-retry-sleep

Sleep before retrying SSH#establish_connection.
help_update: Modify the kitchen help information for the commands that
change instance state.

help_update: Change the help test message for failed execution.

help_update:Fix spelling

help_update: Fix formatting for rubocop errors.
Merge pull request #450 from MarkGibbons/help_update

Help update
typeo confiuration -> configuration
Merge pull request #457 from michaelkirk/patch-1

typeo confiuration -> configuration
Support configuration of client.rb for proxies.

This uses the proxy configuration that is made available and writes it
to the appropriate values in the client.rb file for all of the derived
Chef provisioners.

Also adds support for ssl_verify_mode settings.
Add no_proxy value to environment variables.
Add support for ftp_proxy environment variable.