More improvement to user error message
 * We now show the context in the Vagrantfile where we think the
   error occurred.
 * Updated CHANGELOG
 * Bumped to 1.2.0.dev1
Improved Stack helper module
 * Renamed methods to have better names.
 * Split one method in two parts for better isolation of responsabilities.
 * Added some initial tests for the Stack helper module.
Added new tests for Helper::Stack module
Released version 1.2.0
Bumped to 1.2.1 development version
Merge branch '1.x'

Conflicts:
	lib/nugrant/version.rb