Added first cut of docs for configuring Catch

- initially just covers new colour config
- also updated all [Home] links in footers to go to local readme

docs/configuration.md

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+Catch is designed to "just work" as much as possible. For most people the only configuration needed is telling Catch which source file should host all the implementation code (```CATCH_CONFIG_MAIN```).
+
+Nonetheless there are still some occasions where finer control is needed. For these occasions Catch exposes a small set of macros for configuring how it is built.
+
+#  Terminal colour
+
+Yes, I am English, so I will continue to spell "colour" with a 'u'.
+
+When sending output to the terminal, if it detects that it can, Catch will use colourised text. On Windows the Win32 API, ```SetConsoleTextAttribute```, is used. On POSIX systems ANSI colour escape codes are inserted into the stream.
+
+For finer control you can define one of the following identifiers (these are mutually exclusive - but that is not checked so may behave unexpectedly if you mix them):
+
+	CATCH_CONFIG_COLOUR_NONE	// completely disables all text colouring
+	CATCH_CONFIG_COLOUR_WINDOWS	// forces the Win32 console API to be used
+	CATCH_CONFIG_COLOUR_ANSI	// forces ANSI colour codes to be used
+
+Note that when ANSI colour codes are used "unistd.h" must be includable - along with a definition of ```isatty()```
+
+Typically you should place the ```#define``` before #including "catch.hpp" in your main source file - but if you prefer you can define it for your whole project by whatever your IDE or build system provides for you to do so.
+
+---
+
+[Home](Readme.md)