extract archive into correct directory

Signed-off-by: S.Çağlar Onur <caglar@10ur.org>
diff --git a/Dockerfile b/Dockerfile
index dad71b3..08f4f8d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -79,7 +79,7 @@
 
 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 tar jxvf /usr/local/share/phantomjs-1.7.0-linux-x86_64.tar.bz2 -C /usr/local/share/
 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