Update dependencies

- Updated all the dependencies to support last Grunt release
- Replaced my old customized tasks (bump and markdown) with grunt-bumpx
  and grunt-markdown plugins
Fix config files and sources

- Added the `.md/` directory into .gitignore
- Converted soft tabs to hard tabs
Merge pull request #1 from Ragnarokkr/update-grunt-4

Update dependencies. Fix config and source files.