PayloadEscapeCharacter.MultilineMultipleEscapeCharacterExtraNewline* tests fail distcheck on Travis-CI (Filenames are too long)

From the Travis-CI make distcheck logs:
```bash
tardir=webvtt-0.0.3 && ${TAR-tar} chof - "$tardir" | GZIP=--best gzip -c >webvtt-0.0.3.tar.gz
tar: webvtt-0.0.3/test/unit/payload/escape-character/multiline-multiple-escape-character-extra-newline-cr.vtt: file name is too long (max 99); not dumped
tar: webvtt-0.0.3/test/unit/payload/escape-character/multiline-multiple-escape-character-extra-newline.vtt: file name is too long (max 99); not dumped
tar: webvtt-0.0.3/test/unit/payload/escape-character/multiline-multiple-escape-character-extra-newline-crlf.vtt: file name is too long (max 99); not dumped
tar: Exiting with failure status due to previous errors
```

The distcheck build on Travis fails tests using these files (parse fails), and this is a good hint as to why (particularly because I can't reproduce it on my local system).

Basically these filenames are too long and need to be cut down a bit.