Moving over from watchexec/cargo-watch#67

When respecting gitignore files to not watch, the current implementation only looks at the local .gitignore file, but not other ones that git itself recognizes, specially ~/.gitignore.

The best and common practice to gitignore editor temp files is to put the patters in ~/.gitignore, as they are something user-dependent and not project-dependent (and its hard for projects to stay inclusive to all types of editors and their settings).

Because of this, right now, when using cargo watch, I get a new execution whenever I open/close my editors (VIM), which is very often, because of the .*.swp files being created and dropped.