Merge branch 'patch-1' of https://github.com/stas-sultanov/StackExchange.Redis...

Merge branch 'patch-1' of https://github.com/stas-sultanov/StackExchange.Redis into stas-sultanov-patch-1

Conflicts:
	StackExchange.Redis/StackExchange/Redis/ConfigurationOptions.cs

Note: tweaked a bit

StackExchange.Redis/StackExchange/Redis/ConfigurationOptions.cs

@@ -263,6 +263,8 @@ public CommandMap CommandMap
         /// <summary>
         /// Parse the configuration from a comma-delimited configuration string
         /// </summary>
+        /// <exception cref="ArgumentNullException"><paramref name="configuration"/> is <c>null</c>.</exception>
+        /// <exception cref="ArgumentException"><paramref name="configuration"/> is empty.</exception>
         public static ConfigurationOptions Parse(string configuration)
         {    
             var options = new ConfigurationOptions();
@@ -272,6 +274,8 @@ public static ConfigurationOptions Parse(string configuration)
         /// <summary>
         /// Parse the configuration from a comma-delimited configuration string
         /// </summary>
+        /// <exception cref="ArgumentNullException"><paramref name="configuration"/> is <c>null</c>.</exception>
+        /// <exception cref="ArgumentException"><paramref name="configuration"/> is empty.</exception>
         public static ConfigurationOptions Parse(string configuration, bool ignoreUnknown)
         {
             var options = new ConfigurationOptions();
@@ -456,9 +460,18 @@ void Clear()
 
         private void DoParse(string configuration, bool ignoreUnknown)
         {
-            Clear();
-            if (!string.IsNullOrWhiteSpace(configuration))
+            if (configuration == null)
             {
+                throw new ArgumentNullException("configuration");
+            }
+
+            if (string.IsNullOrWhiteSpace(configuration))
+            {
+                throw new ArgumentException("is empty", configuration);
+            }
+
+            Clear();
+
             // break it down by commas
             var arr = configuration.Split(StringSplits.Comma);
             Dictionary<string, string> map = null;
@@ -561,5 +574,4 @@ private void DoParse(string configuration, bool ignoreUnknown)
             }
         }
     }
-    }
 }