[CI] allow travis to find eigenpy exports

travis_custom/custom_before_install_linux.sh

@@ -8,4 +8,5 @@ sudo apt-get -qqy install robotpkg-py27-eigenpy
 
 # set environment variables
 export PKG_CONFIG_PATH="${PKG_CONFIG_PATH}:/opt/openrobots/lib/pkgconfig"
-export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:/opt/openrobots/lib"
\ No newline at end of file
+export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:/opt/openrobots/lib"
+export CMAKE_PREFIX_PATH="${CMAKE_PREFIX_PATH}:/opt/openrobots"