[purs ide] Add import chomps line on windows

[nwolverson]

Running on windows, with a source file with CRLF line endings, add import seems to be removing a line after the import section. Converting to LF line endings, seems to be fine with everything else unchanged.

e.g.

module Main.Module where

import Prelude
import Control.Monad.Eff.Console (log)
main = do
  log "Hello sailor!"
  logShow

becomes

module Main.Module where

import Prelude
import Control.Monad.Eff.Console (log, logShow)
  log "Hello sailor!"
  logShow

Called as addImport with temp file as input/output

Originally raised as nwolverson/vscode-ide-purescript#52

[paf31]

@kritzcreek Please reprioritize these if you think they're not good for 1.0.