Feature request: Don't assume everyone uses github

[bufke]

Many would prefer to use libre solutions for source control such as self hosted git or gitlab. Currently npm postclone requests a github username. It would probably be fine to just make the git username question optional.
As a workaround it's possible to just enter any name and change it in package.json later.

[radeva]

This name is used as plugin author in the package.json. Will fix the wording so it becomes clearer.