gitignore: ignore generated files
tab -> space

Following coding convention, use spaces rather than tabs.
'erased'-vector must not be bound to class.

If the erased vector is part of the class, it well result in
undefined behavior if the class is deleted during the callback.
Merge branch 'issue/2' into staging

* issue/2:
  'erased'-vector must not be bound to class.
  tab -> space
  gitignore: ignore generated files