Update README.md

Changes:
- Merged parts of the documentation with README.md
- Small fixups/additions to README.md

Author: Robertof

README.md

@@ -1,21 +1,57 @@
 libpifacedigital
 ================
-A simple library for controlling PiFace Digital. See `example.c` for example
-usage. Hides the SPI file descriptors so the user only has to deal with
-`hw_addr`.
+
+A simple library for controlling
+[PiFace Digital](http://www.piface.org.uk/products/piface_digital/).
+Hides the SPI file descriptors so the user only has to deal with `hw_addr`.
+
+Building
+--------
+
+To build the library, first install the required dependency
+[libmcp23s17](https://github.com/piface/libmcp23s17). Then run:
+
+    $ make
+
+Install the library to `/usr/local` using:
+
+    $ make install
+
+To test the library, compile and execute the example program:
+
+    $ make example
+    $ ./example
+
+A command line utility named `pifacedigital` is also available. Build with:
+
+    $ make pifacedigital
+    $ ./pifacedigital read input
+    $ ./pifacedigital --help
+
+Usage
+-----
+
+See `example.c` for example usage.
+
+Compile your software with the following flags:
+
+    -lpifacedigital -lmcp23s17
+
+You can specify the path of the libraries manually, using:
+
+    -I/path/to/headers -L/path/to/libpifacedigital -lpifacedigital -L/path/to/mcp23s17 -lmcp23s17
 
 Documentation
 -------------
 
-[http://piface.github.io/libpifacedigital](http://piface.github.io/libpifacedigital)
+An online version of the documentation is available at http://piface.github.io/libpifacedigital.
 
-Build the docs with:
+Build it with (assuming that you are in the directory of the cloned repository):
 
-    $ git clone https://github.com/piface/libpifacedigital.git
-    $ cd libpifacedigital/docs/
+    $ cd docs/
     $ doxygen pifacedigital-doc.conf
 
-To view as HTML, point your browser to `libpifacedigital/docs/html/index.html`.
+To view as HTML, point your browser to `docs/html/index.html`.
 
 To view as PDF: