Add a pathspider.helpers.tor with connect_tor and connect_http_tor about pathspider

[irl]

This should be done in a similar manner to the MONROE wrapper. The MONROE wrapper can be generalised as it's using Netlink messages for detecting invalidation of results due to link failure, not the proprietary MONROE metadata service. We can build both of these in as seperate entry points, or as command line switches calling wrapper functions.

[meejah]

"very soon", there will be some much nicer interfaces for doing streams-over-a-circuit in txtorcon, so you can get back an IStreamClientEndpoint that will go via a particular circuit on .connect() -- which probably helps for use-cases like this (see the release-1.x branch in txtorcon if you're interested).

[irl]

Thanks @meejah (: That sounds awesome!

[britram]

Implement this as a helper (like #70, #74). Plugins will need to be aware of the fact they're using Tor, but this makes sense.

[meejah]

p.s. the API I spoke of above is in master now as Circuit.stream_via.