Support for INSERT using SELECT about honeysql

[hlship]

Another failed attempt:

(let [user-id 12345
      role-names ["user" "admin"]]
  (-> (insert-into :user_profile_to_role)
      (columns :user_profile_id :role_id)
      (values [
               (-> (select user-id, :r.id)
                   (from [:role :r])
                   (where [:in :role role-names]))])
      sql/format))

=> ["INSERT INTO user_profile_to_role (user_profile_id, role_id) (where, from, select) VALUES (in role, role r NULL, 12345 r.id)"]

[ddellacosta]

Since this is redundant with #33 and there is a pull request now (#50) with a proposal for solving this, going to close this one.