Update readme

Author: colinangusmackay

README.md

@@ -52,6 +52,10 @@ ShortCode.GenerateSequentialShortCode();
 
 // To generate sequential short code of the given length
 ShortCode.GenerateSequentialShortCode(int length);
+
+// To generate a patterned short code
+// by default in the format XXX-XXX-XXX
+ShortCode.GeneratePatternedShortCode();
 ```
 
 There are some configuration methods you can call during your app's startup:
@@ -63,6 +67,15 @@ There are some configuration methods you can call during your app's startup:
   - `GuidCodeGenerator`: The code is a hashed form of a GUID
   - `RandomCodeGenerator`: The code is generated from the `Random` class.
   - `CrytographicallyRandomCodeGenerator`: The code is generated using a cryptographic strength random number generator.
+* `ShortCode.SetPattern(IEnumerable<PatternPart> parts)`: Sets the pattern using the given parts. (See below)
+
+## Pattern Parts
+
+If you are using patterned short codes then you can define the pattern with a collection of `PatternPart`. There are two types of pattern part, a `Fixed` part, which consists of a fixed string; and, a `EncodeIntoCharacterSpace` type, which is part of the encoded short code.
+
+To create the encoding part: `new PatternPart(string characterSpace, int length)`. The character space is a string containing the valid characters that a code can contain. It must be made up of unique characters. The `length` is the length of the encoded sequence.
+
+To create the fixed part: `new PatternPart(string fixedChars)`. Where `fixedChars` is the fixed string that is used to separate parts of the code.
 
 ## Setting up Short Codes with Microsoft's Dependency Injection
 
@@ -143,9 +156,37 @@ In the appsettings.json file:
 }
 ```
 
+If you prefer to use a patterned short code generator the appsettings.json will look something like this:
+
+```json
+{
+  "Stravaig": {
+    "ShortCode": {
+      "Pattern":[{
+        "Type": "EncodeIntoCharacterSpace",
+        "CharacterSpace": "0123456789QWERTYPLKJHGFDSAZXCVBNM",
+        "Length": 4
+      },{
+        "Type": "Fixed",
+        "FixedString": "-"
+      },{
+        "Type": "EncodeIntoCharacterSpace",
+        "CharacterSpace": "0123456789QWERTYPLKJHGFDSAZXCVBNM",
+        "Length": 4
+      }],
+      "Generator": {
+        "Seed": 12345
+      }
+    }
+  }
+}
+```
+
+Note, that when the configuration contains a pattern it overrides any general specification.
+
 ## Using the IShortCodeFactory
 
 To get a short code, the `IShortCodeFactory` interface exposes two methods for to create short codes.
 
 * `GetNextCode()` will simply get the next code.
-* `GetCodes(int)` will return the number of codes specified as an `IEnumerable<string>`
+* `GetCodes(int number)` will return the `number` of codes specified as an `IEnumerable<string>`