Prevent a nasty lockup when bad proxy data is sent

When bad/incomplete data is sent to the proxy protocol, ranch's
'infinity' timeout may cause the parser (with {packet, line}) to never
return. This in turn locks up the server and brings it down without ever
crashing it.

This fix makes it so that a configured timeout (now made much larger)
can be substituted in to replace the 'infinity' value whenever it is
submitted, working around the issue.
Merge pull request #7 from heroku/never-infinity-on-proxy

Prevent a nasty lockup when bad proxy data is sent