mavericks setup instuctions

This is how I remeber to have set up my machine. If anything is
missing (I don't have a virgin machine to test this) please
create a github issue or a pull request (after all, unclean
documentation is what we need to consider a bug!).
If you want to start documenting setup for a new platform like
for instance ubuntu, RHEL or (/me whispers) some flavour of
windows please consider doing so. You should start by creating a
new page and I'll follow suit and move the OS X content also.