Improved configuration handling
 * Better handling in Vagrant of cases where the vagrant user
   file cannot be parsed correctly. This is now reported
   as an error in Vagrant an nicely displayed with the path
   of the offending file and the parser error message.
 * Better handling of how global Nugrant options are passed and
   handled. Everything is now located in the `Nugrant::Config`
   object and used by everything that need some configuration
   parameters.
Added possibility to change array merge strategy
Bumped to 2.0.0.pre2