.travis.yml: Rebuild schema-fs in the Travis tests

And error out if that fails.  'make schema-fs' is in before_install,
since things are really broken in that case and we want to error the
build exit immediately [1].  If someone forgot to run schema-fs,
that's less serious and we only want to fail the build (and still run
the other tests) [1].

[1]: https://docs.travis-ci.com/user/customizing-the-build/#Breaking-the-Build

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

.travis.yml

@@ -16,10 +16,12 @@ before_install:
   - go get -u github.com/alecthomas/gometalinter
   - gometalinter --install
   - go get -t -d ./...
+  - make schema-fs
 
 install: true
 
 script:
+  - git diff-files --exit-code
   - env | grep TRAVIS_
   - make .gitvalidation
   - make lint