Exclude Path Flag

[pjdufour]

Adds an --exclude-path or -e flag for exclude files or directories, such as -e gulpfile.js -e package.json -e node_modules/. Only works with embed-go action.

[GeertJohan]

It must either work for all methods, or become an option to the embed command. But I prefer keeping this consistent across bundling methods.

[GeertJohan]

@pjdufour Please let me know if you want to pick this PR up again? There's discussion in #83 about an ignore file as well, although that may co-exist with a flag option.