Create README.md file for viewing on github.

This is a lightly edited README using github's MARKDOWN.

Submitted by:	Johan <johan2422@gmail.com>
Pull Request:	https://github.com/freebsd/freebsd/pull/56

README.md

+FreeBSD Source:
+---------------
+This is the top level of the FreeBSD source directory.  This file  
+was last revised on:  
+$FreeBSD$
+
+For copyright information, please see the file COPYRIGHT in this  
+directory (additional copyright information also exists for some    
+sources in this tree - please see the specific source directories for  
+more information).
+
+The Makefile in this directory supports a number of targets for  
+building components (or all) of the FreeBSD source tree.  See build(7)  
+and http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html  
+for more information, including setting make(1) variables.  
+
+The `buildkernel` and `installkernel` targets build and install  
+the kernel and the modules (see below).  Please see the top of  
+the Makefile in this directory for more information on the  
+standard build targets and compile-time flags.
+
+Building a kernel is a somewhat more involved process.  See build(7), config(8),  
+and http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html  
+for more information.
+
+Note: If you want to build and install the kernel with the  
+`buildkernel` and `installkernel` targets, you might need to build  
+world before.  More information is available in the handbook.
+
+The kernel configuration files reside in the `sys/<arch>/conf`  
+sub-directory.  GENERIC is the default configuration used in release builds.  
+NOTES contains entries and documentation for all possible  
+devices, not just those commonly used.
+
+
+Source Roadmap:
+---------------
+```
+bin				System/user commands.
+
+cddl			Various commands and libraries under the Common Development  
+				and Distribution License.
+
+contrib			Packages contributed by 3rd parties.
+
+crypto			Cryptography stuff (see crypto/README).
+
+etc				Template files for /etc.
+
+gnu				Various commands and libraries under the GNU Public License.  
+				Please see gnu/COPYING* for more information.
+
+include			System include files.
+
+kerberos5		Kerberos5 (Heimdal) package.
+
+lib				System libraries.
+
+libexec			System daemons.
+
+release			Release building Makefile & associated tools.
+
+rescue			Build system for statically linked /rescue utilities.
+
+sbin			System commands.
+
+secure			Cryptographic libraries and commands.
+
+share			Shared resources.
+
+sys				Kernel sources.
+
+tests			Regression tests which can be run by Kyua.  See tests/README
+				for additional information.
+
+tools			Utilities for regression testing and miscellaneous tasks.
+
+usr.bin			User commands.
+
+usr.sbin		System administration commands.
+```
+
+For information on synchronizing your source tree with one or more of  
+the FreeBSD Project's development branches, please see:
+
+   http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html