Add tox config for running unit tests. (#702)

The setup.py test command is deprecated, and tox is the replacement.
diff --git a/.gitignore b/.gitignore
index e01da94..9c7984a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@
 .pytest_cache/
 .sass-cache
 _site
+.tox/
diff --git a/README.md b/README.md
index 27fd73a..da91264 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,19 @@
 * [Mobly AndroidDevice Service](docs/android_device_service.md) -
 Create custom service to attach to Mobly's `AndroidDevice` controller.
 
+## Test
+To run the unit tests for Mobly to verify your local changes:
+
+Make sure you have `tox` installed:
+```sh
+pip install tox
+```
+
+Then in the Mobly directory, run:
+```sh
+tox
+```
+
 ## Mobly Snippet
 The Mobly Snippet projects let users better control Android devices.
 
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..741b2ac
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,11 @@
+[tox]
+envlist = py3
+
+[testenv]
+deps =
+    pytest
+    mock
+    pytz
+commands =
+    pytest
+