ReturnCode always 0 when run against multiple globs

If you use multiple glob patterns, write-good will always return 0 even if there's grammar mistakes.

This is what happens when using multiple globs, `*.md` and `./docs/*.md`:
Example
```bash
$ write-good *.md ./docs/*.md --parse --no-passive --no-adverb --no-tooWordy --no-cliches
README.md:14:29:"various" is a weasel word
README.md:15:6:"and" is repeated

$ echo $?
0
```

Whereas this is what happens when run with only one glob, `*.md`:
```bash
$ write-good *.md --parse --no-passive --no-adverb --no-tooWordy --no-cliches
README.md:14:29:"various" is a weasel word
README.md:15:6:"and" is repeated
$ echo $?
255
```

Start by reproducing the reported command with multiple glob patterns and compare its exit status with the single-glob command. Trace the CLI's glob-processing and return-code handling; done means grammar findings from any matched file produce a nonzero exit status, with coverage for multiple globs.

Written by the indexing model from the issue text.