added stuff for CI

.travis.yml

@@ -2,4 +2,6 @@ dist: xenial
 language: python
 python:
         - 3.7
-script: make test
+before_install:
+  - sudo apt-get -y install tor
+script: make test

requirements.in

@@ -0,0 +1 @@
+stem

requirements.txt

@@ -4,3 +4,6 @@
 #
 #    pip-compile --generate-hashes --output-file=requirements.txt requirements.in
 #
+stem==1.8.0 \
+    --hash=sha256:a0b48ea6224e95f22aa34c0bc3415f0eb4667ddeae3dfb5e32a6920c185568c2 \
+    # via -r requirements.in