Fixed how to check the OS type.

``$OSTYPE`` is "FreeBSD" in FreeBSD 8.2 and this does not match ``*'bsd'*``.
Therefore ``$SHELL_PLATFORM`` will be "unknown".

As a result, weather.sh will access to weather.yahooapis.com every 15 seconds (It depends on ``status-interval`` of tmux setting).

\# I'm not good at English...please forgive me.