added force flag to appveyor npm install command, fixes https://github.com/npm/npm/issues/9696 https://github.com/Microsoft/vsts-tasks/issues/323
added force flag to appveyor npm install command, fixes https://github.com/npm/npm/issues/9696 https://github.com/Microsoft/vsts-tasks/issues/323

MoOx/markdown-it-toc-and-anchor,medfreeman/markdown-it-toc-and-anchor