Vagrant のバージョンアップ
Use the boxen-git-credential for all repositories clones.

This is required since puppet run all the comands as root and the
credential config is only present on the user land.

The lack of this configuration is making clones using https to not
work since the credential is not present for the root.

Closes #286
Merge pull request #305 from rafaelfranca/rm-fix-repository-clone

Use the boxen-git-credential for all repositories clones.
Update line highlighting
Replace dashes by underscores in GitHub usernames
Add note about GitHub usernames with dashes in README
Merge pull request #310 from benja-M-1/master

Replace dashes by underscores when generating personal manifest
Merge branch 'master' of https://github.com/boxen/our-boxen