remove version number

Author: timmyliu

.travis.yml

@@ -43,7 +43,7 @@ addons:
       # boost-latest contains boost v1.55
       - boost-latest
     packages:
-      - gfortran-4.9
+      - gfortran
       # g++-4.8 is minimum version considered to be the first good c++11 gnu compiler
       # - g++-4.8
       # - clang-3.6