ARes can has timeout (patch reviews requested)

I've been using a lot of APIs in my Ruby (usually Rails) applications
and I've learnt my lesson regarding socket timeouts. Basically, no
response (from an API) is better than a slow response. In the cases of
slow responses, it's better to time out so your ActiveResource clients
can end execution fast (i.e. fail-fast) instead of blocking (for the
default Net::HTTP read_timeout value of 60 seconds) and locking up an
entire web server process.

So the patches for ActiveResource:

* Introduce ActiveResource::Base.timeout to allow
Net::HTTP#read_timeout to be set -
* ActiveResource::Connection should rescue from Timeout::Error -

Please take a look and share any comments/improvements and feel free
to point out any flaws and laugh at my code.

Chu Yeow