observer raises expections when phantomjs is missing

Signed-off-by: S.Çağlar Onur <caglar@10ur.org>
diff --git a/Dockerfile b/Dockerfile
index d84e66a..dad71b3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -77,6 +77,13 @@
 RUN git clone git://git.planet-lab.org/fofum.git /tmp/fofum
 RUN cd /tmp/fofum; python setup.py install
 
+RUN mkdir -p /usr/local/share /bin
+ADD http://phantomjs.googlecode.com/files/phantomjs-1.7.0-linux-x86_64.tar.bz2 /usr/local/share/
+RUN tar jxvf /usr/local/share/phantomjs-1.7.0-linux-x86_64.tar.bz2
+RUN rm -f /usr/local/share/phantomjs-1.7.0-linux-x86_64.tar.bz2
+RUN ln -s /usr/local/share/phantomjs-1.7.0-linux-x86_64 /usr/local/share/phantomjs
+RUN ln -s /usr/local/share/phantomjs/bin/phantomjs /bin/phantomjs
+
 # Get XOS 
 ADD planetstack /opt/xos