gem_source: Add a provisioner gem_source option to allow for a local gem
source.  Busser and related gems may be installed from this source.
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
gem_source: Remove the default gem_source if adding a new one.
A bug exists in gem processing so that if the search for a gem
fails in one source the search is abandoned and the next source
is not used.  A newer version of chef may include a version of
ruby where this issue is fixed. chef 11.4.0 is broken.
typeo confiuration -> configuration
Merge pull request #457 from michaelkirk/patch-1

typeo confiuration -> configuration
Merge branch 'master' of https://github.com/test-kitchen/test-kitchen into gem_source
Merge branch 'gem_source' of https://github.com/MarkGibbons/test-kitchen into gem_source

Conflicts:
	CHANGELOG.md
	lib/kitchen/provisioner/chef_base.rb