add pdns table schema
run specs with bundle exec in Guardfile

I got some errors with incompatible rspecs version.
This fixes the issues.
fix some trailing whitespaces
add AnnotateModels - see: https://github.com/ctran/annotate_models
fix some factory_girl issues
Merge branch 'feature/add_pdns_tables' of github.com:pgolm/DNSHub into feature/add_pdns_tables

Conflicts:
	Gemfile
	README.md
add validation to domain model
fix some factory_girl issues
run db:migrate in test env on travis
Merge branch 'feature/domain_validation' of github.com:pgolm/DNSHub into feature/domain_validation