Suppress Vim error on 'replace_all'

Vim throws E753 when `:spellrepall` finds no more instance of the word
to correct; this is not useful in the context of our Unite source action.
Handle '-no-split' usage with 'startofline' set

Fixes #1. Reverts 9a15df30f59bcdc7602df7dfebed381daba37c59.