Removed uncompatible gem install flag

The latest version of gem removed the flag "includes-dependencies".
It's now the default behavior in gem 2.0.0

Author: Nicolas Lupien

lib/puppet/provider/rvm_gem/gem.rb

@@ -72,8 +72,8 @@ def self.gemsplit(desc)
   def install(useversion = true)
     command = gembinary + ['install']
     command << "-v" << resource[:ensure] if (! resource[:ensure].is_a? Symbol) and useversion
-    # Always include dependencies
-    command << "--include-dependencies"
+    # Dependencies are now installed by default
+    # command << "--include-dependencies"
 
     if source = resource[:source]
       begin