Allow whitespace before single-line comments

[philschatz]

useful for LESS/SCSS which allow scoped selectors and namespaces

For example:

// # Util mixins
// Various mixins that are sprinkled into other selectors
#utils {

  // ## Page Breaks
  #pb {

    // Break before the current element
    .before(@avoid) {
      /* Some rules ... */
    }
  }  
}

Aside: This is being used in conjunction with https://github.com/philschatz/css-coverage.js