Support @overload tag

[netzpirat]

Describe that your method can be used in various contexts with various parameters or return types. The first line should declare the new method signature, and the following indented tag data will be a new documentation string with its own tags adding metadata for such an overload.

class Store
  # @overload set(key, value)
  #   Sets a value on key
  #   @param [Symbol] key describe key param
  #   @param [Object] value describe value param
  # @overload set(value)
  #   Sets a value on the default key `:foo`
  #   @param [Object] value describe value param
  set: (args...) ->