Use Sphinx for documentation

See #60

docs/usage.rst

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+Usage
+=====
+- Forward all traffic::
+
+      sshuttle -r username@sshserver 0.0.0.0/0
+
+- By default sshuttle will automatically choose a method to use. Override with
+  the ``--method=`` parameter.
+
+- There is a shortcut for 0.0.0.0/0 for those that value
+  their wrists::
+
+      sshuttle -r username@sshserver 0/0
+
+- If you would also like your DNS queries to be proxied
+  through the DNS server of the server you are connect to::
+
+      sshuttle --dns -r username@sshserver 0/0
+
+  The above is probably what you want to use to prevent
+  local network attacks such as Firesheep and friends.
+
+(You may be prompted for one or more passwords; first, the local password to
+become root using sudo, and then the remote ssh password.  Or you might have
+sudo and ssh set up to not require passwords, in which case you won't be
+prompted at all.)
+
+
+Usage Notes
+-----------
+That's it!  Now your local machine can access the remote network as if you
+were right there.  And if your "client" machine is a router, everyone on
+your local network can make connections to your remote network.
+
+You don't need to install sshuttle on the remote server;
+the remote server just needs to have python available. 
+sshuttle will automatically upload and run its source code
+to the remote python interpreter.
+
+This creates a transparent proxy server on your local machine for all IP
+addresses that match 0.0.0.0/0.  (You can use more specific IP addresses if
+you want; use any number of IP addresses or subnets to change which
+addresses get proxied.  Using 0.0.0.0/0 proxies *everything*, which is
+interesting if you don't trust the people on your local network.)
+
+Any TCP session you initiate to one of the proxied IP addresses will be
+captured by sshuttle and sent over an ssh session to the remote copy of
+sshuttle, which will then regenerate the connection on that end, and funnel
+the data back and forth through ssh.
+
+Fun, right?  A poor man's instant VPN, and you don't even have to have
+admin access on the server.
+
+Additional information for TPROXY
+---------------------------------
+TPROXY is the only method that supports full support of IPv6 and UDP.
+
+Full UDP or DNS support with the TPROXY method requires the ``recvmsg()``
+syscall. This is not available in Python 2, however is in Python 3.5 and
+later. Under Python 2 you might find it sufficient installing PyXAPI_ to get
+the ``recvmsg()`` function.
+
+There are some things you need to consider for TPROXY to work:
+
+- The following commands need to be run first as root. This only needs to be
+  done once after booting up::
+
+      ip route add local default dev lo table 100
+      ip rule add fwmark 1 lookup 100
+      ip -6 route add local default dev lo table 100
+      ip -6 rule add fwmark 1 lookup 100
+
+- The ``--auto-nets`` feature does not detect IPv6 routes automatically. Add IPv6
+  routes manually. e.g. by adding ``'::/0'`` to the end of the command line.
+
+- The client needs to be run as root. e.g.::
+
+      sudo SSH_AUTH_SOCK="$SSH_AUTH_SOCK" $HOME/tree/sshuttle.tproxy/sshuttle  --method=tproxy ...
+
+- You may need to exclude the IP address of the server you are connecting to.
+  Otherwise sshuttle may attempt to intercept the ssh packets, which will not
+  work. Use the ``--exclude`` parameter for this.
+
+- Similarly, UDP return packets (including DNS) could get intercepted and
+  bounced back. This is the case if you have a broad subnet such as
+  ``0.0.0.0/0`` or ``::/0`` that includes the IP address of the client. Use the
+  ``--exclude`` parameter for this.
+
+- You need the ``--method=tproxy`` parameter, as above.
+
+- The routes for the outgoing packets must already exist. For example, if your
+  connection does not have IPv6 support, no IPv6 routes will exist, IPv6
+  packets will not be generated and sshuttle cannot intercept them::
+
+      telnet -6 www.google.com 80
+      Trying 2404:6800:4001:805::1010...
+      telnet: Unable to connect to remote host: Network is unreachable
+
+  Add some dummy routes to external interfaces. Make sure they get removed
+  however after sshuttle exits.