iterator: IteratorSeeker should only contains 'seeks method' to better explain what 'seeks method' is
journal: Fix journal reader that may returns invalid io.ErrUnexpectedEOF error

This fix journal reader that returns io.ErrUnexpectedEOF error due to
'chunk length overflows block' when strict == false.

As reported at conformal/btcd#18.
Merge branch 'master' into marco_merge_upstream20131015