(travis) Do not install things bring with conan already

.travis/install.sh

@@ -3,12 +3,12 @@ set -e # Enables cheking of return values from each command
 set -x # Prints every command
 
 if [[ "$(uname -s)" == 'Linux' ]]; then
-    sudo apt-get install cmake zlib1g-dev libssh-dev libcurl4-openssl-dev gettext libexpat1-dev
+    sudo apt-get install cmake zlib1g-dev libssh-dev gettext
     sudo apt-get install python-pip libxml2-utils
     sudo pip install virtualenv
 else
     brew update
-    brew install expat gettext libssh
+    brew install gettext libssh
     brew install pyenv-virtualenv
     # By default it already has cmake 3.6.2
 fi