use system ipython on ubuntu 15+

Author: cb

install-deps

@@ -145,12 +145,12 @@ elif [[ "$(uname)" == 'Linux' ]]; then
         elif [[ $ubuntu_major_version -lt '14' ]]; then
             sudo add-apt-repository -y ppa:chris-lea/zeromq
             sudo add-apt-repository -y ppa:chris-lea/node.js
+        elif [[ $ubuntu_major_version -lt '15' ]]; then
+            sudo add-apt-repository -y ppa:jtaylor/ipython
         else
             sudo apt-get install -y software-properties-common \
                 libgraphicsmagick1-dev nodejs npm libfftw3-dev sox libsox-dev \
                 libsox-fmt-all
-
-            sudo add-apt-repository -y ppa:jtaylor/ipython
         fi
 
         gcc_major_version=$(gcc --version | grep ^gcc | awk '{print $4}' | \