add /ruleset as a command line switch for FxCop task. Added RuleSet property to be set from MSBuild.

Author: jricke

Source/MSBuild.Community.Tasks/FxCop.cs

@@ -187,7 +187,15 @@ public ITaskItem[] Rules
         {
             get { return _rules; }
             set { _rules = value; }
-        }
+        }
+
+        /// <summary>
+        /// Gets or sets the rule set.
+        /// </summary>
+        /// <value>
+        /// The rule set.
+        /// </value>
+        public string RuleSet { get; set; }
 
         private string _analysisReportFileName;
 
@@ -484,6 +492,11 @@ protected override string GenerateCommandLineCommands()
                 }
             }
 
+            if (!string.IsNullOrEmpty(RuleSet))
+            {
+                _programArguments.AppendFormat("/ruleset:{0} ", RuleSet);
+            }
+
             if (IncludeSummaryReport)
             {
                 _programArguments.Append("/s ");