Enable to delete more freely with backspace

ref. http://qiita.com/omega999/items/23aec6a7f6d6735d033f
Hilighte local variables in Ruby

ref.
  http://www.todesking.com/blog/2014-04-29-highlight-ruby-local-variables-in-vim/
  https://github.com/todesking/ruby_hl_lvar.vim
Merge branch 'ruby-hl-lvar'