(CONT-1001) Add litmus ~> 1.0

Author: Ramesh7

Diff for: Gemfile

@@ -37,7 +37,7 @@ group :development do
   gem "github_changelog_generator", '= 1.15.2',    require: false
 end
 group :system_tests do
-  gem "puppet_litmus", '< 1.0.0', require: false, platforms: [:ruby, :x64_mingw]
+  gem "puppet_litmus", '~> 1.0', require: false, platforms: [:ruby, :x64_mingw]
   gem "serverspec", '~> 2.41',    require: false
 end