Add txtorcon for tahoe over tor

src/freedombone-app-tahoelafs

     venv/bin/pip install setuptools==11.3
     venv/bin/pip install six==1.10.0 packaging==16.8 attrs==16.3.0 appdirs==1.4.2 pycrypto==2.1.0 cffi==1.9.1
     venv/bin/pip install cryptography==1.7.2 markerlib==0.6.0 distribute==0.7.3
+    venv/bin/pip install txtorcon==0.18.0
     venv/bin/pip install --editable .
     configure_firewall_for_tahoelafs