Fixed FreeBSD-Part of README

[mrdsam]

/usr/src is not required

[RincewindsHat]

ok, works for me. I personally would remove the $ prompt in front of the code lines to be a) consistent with the linunx guide and b) be able to c&p the whole thing.
Would you disagree or like to change that? :-)

[mrdsam]

I agree, remove the $s. It's a personal habit to distinguish commands from command output.

[RincewindsHat]

Thank you :-)