code: function walkGlobal (taskName) {
    // Skip dot operator and tasks that start with a dot.
    if (taskName.indexOf('.') === 0) return
  
    // Skip stuff that may include dots:
    // * comments
    // * strings
    // * numbers
    // * references
    if (regexComment.test(taskName)) return
    if (parseFloat(taskName)) return
    if (regexQuoted.test(taskName)) return
    if (regexReference.test(taskName)) return
  
    function toNextProp (next, prop) {
      return next[prop]
    }
  
    return taskName.split('.')
      .reduce(toNextProp, globalContext)
  }
docs: Walk through global context.
  
  process.version will return global[process][version]
  
  @param {String} taskName
  @returns {*} leaf