README: reference version 2.4 of the maven-archetype-plugin
README: reference version 2.4 of the maven-archetype-plugin

The 3.0.0 version of the maven-archetype-plugin has introduced a new
feature ( or enhancement, but let's not be pedantic ) which means
we need to add remote repositories to ~/.m2/settings.xml .

I think this is too big of a hassle, so we will just reference an
older version of the plugin in the README for using remote
repositories.

See also https://issues.apache.org/jira/browse/ARCHETYPE-519

Fixes #76

MyAccInt/aem-project-archetype,khakiout/aem-project-archetype,khakiout/aem-project-archetype,MyAccInt/aem-project-archetype,Adobe-Marketing-Cloud/aem-project-archetype,Adobe-Marketing-Cloud/aem-project-archetype,Adobe-Marketing-Cloud/aem-project-archetype,khakiout/aem-project-archetype,MyAccInt/aem-project-archetype