Added instructions for how to get the stable_0.4.2 branch.  Added a backslash to the boost b2 command so people can copy and paste the command.
Added instructions for how to get the stable_0.4.2 branch.  Added a backslash
to the boost b2 command so people can copy and paste the command.

senadj/yacoin,yacoin/yacoin,yacoin/yacoin,senadj/yacoin,yacoin/yacoin,senadj/yacoin,ya4-old-c-coder/yacoin,ya4-old-c-coder/yacoin,senadj/yacoin,ya4-old-c-coder/yacoin,ya4-old-c-coder/yacoin,senadj/yacoin,yacoin/yacoin,yacoin/yacoin,ya4-old-c-coder/yacoin