Update README testing info about FreeBSD

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Update README

Detail i386/amd64 as tested for FreeBSD.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Add MIPS to README

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>