Updated toString docs with StringMaker

docs/tostring.md

@@ -1,7 +1,7 @@
 # String conversions
 
 Catch needs to be able to convert types you use in assertions and logging expressions into strings (for logging and reporting purposes).
-Most built-in or std types are supported out of the box but there are two ways that you can tell Catch how to convert your own types (or other, third-party types) into strings.
+Most built-in or std types are supported out of the box but there are three ways that you can tell Catch how to convert your own types (or other, third-party types) into strings.
 
 ## operator << overload for std::ostream
 
@@ -41,6 +41,20 @@ namespace Catch {
 
 Again ```T``` is your type and ```convertMyTypeToString``` is where you'll write whatever code is necessary to make your type printable. Note that the function must be in the Catch namespace, which itself must be in the global namespace.
 
+## Catch::StringMaker<T> specialisation
+
+There are some cases where overloading toString does not work as expected. Specialising StringMaker<T> gives you more precise, and reliable, control - but at the cost of slightly more code and complexity:
+
+```
+namespace Catch {
+	template<> struct StringMaker<T> {
+    	static std::string convert( T const& value ) {
+        	return convertMyTypeToString( value ); 
+        } 
+    }; 
+}
+```
+
 ---
 
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