Dockerfile: Bump CNVkit version to 0.9.6

docker/Dockerfile

@@ -17,7 +17,7 @@ RUN apt-get install -y \
     python-tk \
     zlib1g-dev
 RUN pip install -U future futures pandas pomegranate pyfaidx pysam
-RUN pip install cnvkit==0.9.5
+RUN pip install cnvkit==0.9.6
 # Let matplotlib build its font cache
 RUN cnvkit.py version