add slug

cookiecutter.json

 {
     "full_name": "Abstract Equals Magic",
-    "email": "",
     "github_username": "abstractequalsmagic",
     "project_name": "boilpy",
-    "app_name": "boilpy",
+    "project_slug": "{{ cookiecutter.project_name.lower().replace(' ', '_').replace('-', '_') }}",
     "project_short_description": "Boilerplate for A -eq M applications.",
     "version": "0.0.1"
 }