Add configurability (and documentation) to environment model

[cluesque]

In my environment I want all TCPConnections to go through the proxy if they're bound for the real internet (say, paypal), but not if they're staying inside my firewalled net (memcached, etc.)

This allows that.

Environment variable PROXY_FILTER_LIST is a comma separated list of hosts (or IPs) to not use the proxy with
(e.g. '10.0.0.1,10.0.2.1')

Environment variable PROXY_FILTER_REGEXP is a regular expression, where if the host matches, it connects directly, not through the proxy
(e.g., '(10..*|localhost)')

[samuelkadolph]

I only planned on supporting the basic proxy environment variables (mainly from curl). I'm kind of against adding more unless they are widely used and do something substantial.

Did you just want this for ruby side? Because I could definitely imagine this.

require "proxifier/env"
TCPSocket.environment_no_proxy = proc { |host| host =~ /blah/ }