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
Set the global node version in the site manifest
Merge pull request #311 from smcnabb/master

Set the global node version in the site manifest
Revert "Merge pull request #311 from smcnabb/master"

This reverts commit 40de1e40f3e3c5d47d157c1f996a2a21f033a113, reversing
changes made to 206dee9965730738b0c6011e271950ebfa329d75.

Reason: This make harder to override the global version if it is
required for someone.

See https://github.com/boxen/our-boxen/pull/311#issuecomment-19719152
Merge branch 'master' of https://github.com/boxen/our-boxen