tor: streamline package to better follow the Effective Go guidelines

In this commit, we clean up the tor package to better follow the
Effective Go guidelines. Most of the changes revolve around naming,
where we'd have things like `torsvc.TorDial`. This was simplified to
`tor.Dial` along with many others.

tor/README.md

@@ -0,0 +1,15 @@
+tor
+===
+
+The tor package contains utility functions that allow for interacting with the
+Tor daemon. So far, supported functions include routing all traffic over Tor's
+exposed socks5 proxy and routing DNS queries over Tor (A, AAAA, SRV). In the
+future more features will be added: automatic setup of v2 hidden service
+functionality, control port functionality, and handling manually setup v3 hidden
+services.
+
+## Installation and Updating
+
+```bash
+$ go get -u github.com/lightningnetwork/lnd/tor
+```