Force error return code from `kwalify`.

Kwalify doesn't return a non-0 code of its own accord even if its
validation fails, so this commits adds a hack to .travis.yml that counts
the lines of a quieted kwalify output and uses that number for return
code, which means that a non-err'ing run will return 0 (0 lines) and
runs with errors will return an exit code equivalent to the number of
errors + 1 (the filename of the file containing the errors).