fast-fail for Travis when upon encountering whitespace error

[av skip]

.travis.yml

@@ -41,7 +41,7 @@ before_install:
         make $BUILDOPTS -C contrib -f repackage_system_suitesparse4.make;
       fi
 script:
-    - make check-whitespace
+    - make check-whitespace || exit 1
     - make $BUILDOPTS prefix=/tmp/julia install
     - if [ `uname` = "Darwin" ]; then
         for name in spqr umfpack colamd cholmod amd suitesparse_wrapper; do