simplify how development dependencies are declared
simplify how development dependencies are declared

follows the spec reference defined in http://guides.rubygems.org/specification-reference/

javanthropus/ruby-net-ldap,bkeepers/ruby-net-ldap,javanthropus/ruby-net-ldap,astockwell/ruby-net-ldap,astockwell/ruby-net-ldap,bkeepers/ruby-net-ldap,cloudvolumes/ruby-net-ldap,cloudvolumes/ruby-net-ldap