Implement a wrapper method for MAPADDRESS requests

Implemented the map address wrapper method here.

Things to mention:

Changed "SocksPort 0" to "SocksPort 29327" from the base torrc. (29327 is random)
I wrote an external_ip() function in test.utils (a new file) which I'm not using right now. I'll be using this in a bunch of tests soon. It depends on http://ifconfig.me/ip being up.

Related: spec.

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