Log Message:
net/ruby-net-smtp: add version 0.3.

devel/ruby-redmine51 require net-imap gem version 0.3.3 but ruby31 bundles
0.3.1.  So, it add latest version of net-smtp gem 0.3.3 as ruby-net-smtp.

No version change from deleted ruby-net-pop pacakge.

Simple Mail Transfer Protocol client library for Ruby.