Add .gitignore to lintFiles

First step is to check for a `.gitignore` file in the repo.

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As @basicallydan suggested in PR #38, perhaps a linter for common error files like:
- `.DS_Store`
- `.Trashes`
- `.Spotlight-V100`
- `.idea`
- `*.sublime-*`

What do you think of adding a lintIgnore or something like that?