[vcloud_director] Add get_supported_versions request.

lib/fog/vcloud_director/compute.rb

@@ -107,6 +107,7 @@ module Fog
       request :post_vapp_undeploy
       request :delete_vapp
       request :get_current_session
+      request :get_supported_versions
 
       class Model < Fog::Model
         def initialize(attrs={})

tests/vcloud_director/requests/compute/versions_tests.rb

@@ -0,0 +1,28 @@
+Shindo.tests('Compute::VcloudDirector | versions requests', ['vclouddirector']) do
+
+  SUPPORTED_VERSIONS_FORMAT = {
+    :xmlns => 'http://www.vmware.com/vcloud/versions',
+    :xmlns_xsi => 'http://www.w3.org/2001/XMLSchema-instance',
+    :xsi_schemaLocation => String,
+    :VersionInfo => [{
+      :Version => String,
+      :LoginUrl => String,
+      :MediaTypeMapping => [{
+        :MediaType => String,
+        :ComplexTypeName => String,
+        :SchemaLocation => String
+      }]
+    }]
+  }
+
+  @service = Fog::Compute::VcloudDirector.new
+
+  tests('#get_supported_versions').formats(SUPPORTED_VERSIONS_FORMAT) do
+    @versions = @service.get_supported_versions.body
+  end
+
+  tests('API 5.1 is supported').returns(true) do
+    !!@versions[:VersionInfo].detect {|i| i[:Version] == '5.1'}
+  end
+
+end