serverspec update broke rspec-system-serverspec

[3flex]

Test failure (there may be others depending on what's being required and where, I haven't checked):

lib/rspec-system-serverspec/backend/rspec_system.rb:1:in `require': cannot load such file -- serverspec/backend/exec (LoadError)

Root cause is this Severspec change mizzy/serverspec@b121291

Suggest updating serverspec dependency of this gem to ~> 0.11.0 in Gemspec and pushing a new release until the code's updated.

#3 (comment) seems prescient :)

[3flex]

Fixed by #9