0.5.1: Fix broken .git in npm bundle

Fixes an issue where 0.5.0 would not uninstall from npm.

If you end up in this case, you can fix it by:

1. deleting your node modules
   • or just deleting any .git folders in your simple-markdown dependency
2. bumping your simple-markdown version to 0.5.1 or later
3. running npm install