Disable modifier

[nandi95]

• I'm submitting a ...
  [ ] bug report
  [x] feature request
  [ ] question about the decisions made in the repository
  [ ] question about how to use this project

• Summary
  Add modifier which disables html elements that can take the disabled attribute, e.g.: input, button
  It would look like
  <input v-can.disable="edit-post" />
  meaning if the user cannot edit-post, the input is disabled