Revert "Revert "Removed vim mode lines.""

This reverts commit af77b5b59456f6a9c7a9c6a5464001ef5665f897.

See discussion at
  https://github.com/open-source-parsers/jsoncpp/commit/32009b17e4d35a812575cfcf6bae9ec49fc67446#commitcomment-7827708