Moderate vulnerability in marked dependency

[drinchev]

I found that the project has a moderate vulnerability with one of the dependencies :

  Moderate        Regular Expression Denial of Service

  Package         marked

  Patched in      >=0.6.2

  Dependency of   stylemark [dev]

  Path            stylemark > marked

  More info       https://npmjs.com/advisories/812

I can make a PR if you like.