Travis: use --keep-going with make

This will run all the checks, not stopping at the first failure.

Author: blueyed

.travis.yml

@@ -34,7 +34,7 @@ script:
   - uname -a
   - which -a vim
   - vim --cmd version --cmd quit
-  - make $MAKE_TARGET
+  - make --keep-going $MAKE_TARGET
 
 after_success:
   - covimerage write_coverage $TEST_PROFILE