tidying up some docs in the Extensions namespace

Octokit/Models/Response/CodeFrequency.cs

@@ -6,9 +6,16 @@ using System.Linq;
 
 namespace Octokit
 {
+    /// <summary>
+    /// Represents the summary of lines added and deleted
+    /// </summary>
     [DebuggerDisplay("{DebuggerDisplay,nq}")]
     public class CodeFrequency
     {
+        /// <summary>
+        /// Construct an instance of CodeFrequency
+        /// </summary>
+        /// <param name="rawFrequencies">Raw data </param>
         public CodeFrequency(IEnumerable<IList<long>> rawFrequencies)
         {
             Ensure.ArgumentNotNull(rawFrequencies, "rawFrequencies");