Make travis use docker and update readme.

.travis.yml

@@ -1,5 +1,4 @@
-language: python
-script: |
-  ./setup.py install
-  pip install -r requirements-dev.txt
-  nosetests
+sudo: required
+services:
+  - docker
+script: ./test.sh

Dockerfile

@@ -5,7 +5,7 @@ MAINTAINER github.com/banga/powerline-shell
 ENV USER docker
 ENV USERNAME "Docker User"
 
-# Create a 'docker' user because we might not want to run everything as 'root'. Use 9999 as the ID
+# Create a 'docker' user because we do not want to run everything as 'root'. Use 9999 as the ID
 # to keep it specific and away from the IDs in the host system.
 RUN addgroup -g 9999 $USER && \
     adduser -u 9999 -G $USER -g "$USERNAME" -s /bin/bash -D $USER
@@ -33,7 +33,8 @@ RUN bzr whoami "$USERNAME <$USER@example.com>" && \
 
 COPY . ./
 USER root
-RUN chown -R docker:docker .
+RUN ./setup.py install && \
+    chown -R docker:docker .
 
 USER docker
-RUN nosetests
+ENTRYPOINT ["/bin/sh"]

README.md

@@ -256,8 +256,10 @@ Make sure you introduce new default colors in `themes/default.py` for every new
 segment you create. Test your segment with this theme first.
 
 You should add tests for your segment as best you are able. Unit and
-integration tests are both welcome. Run your tests with the `nosetests` command
-after install the requirements in `requirements-dev.txt`.
+integration tests are both welcome. Run your tests by running the `test.sh`
+script. It uses `docker` to manage dependencies and the environment.
+Alternatively, you can run the `nosetests` command after installing the
+requirements in `requirements-dev.txt`.
 
 ## Troubleshooting
 

test.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+docker build -t powerline-shell .
+docker run --rm -it powerline-shell -c nosetests