Import net-http gem

[herwinw]

This is going to be a long project to get some HTTP connectivity working, mostly to add the essential functionality to OpenSSL. I've added a simple script that I want to get working:

require 'net/http'

puts Net::HTTP.get(URI('http://natalie-lang.org/'))
puts Net::HTTP.get(URI('https://natalie-lang.org/specs'))

I've taken some shortcuts with some required modules. It tried to import the Timeout gem, but this far it only used the exceptions from this code, so I've just limited this file to the exceptions and removed all the other dependencies in timeout.