Note in readme for OS X users how to fix 'too many clients' error when running tests.

Noted in readme need to:

set:
    max_connections = 40

To get this to work you will also need to change your kernel's shared memory
parameters. You can do this by running these shell commands:

    sudo sysctl -w kern.sysv.shmmax=8388608
    sudo sysctl -w kern.sysv.shmall=2048