Log Message:
mikutter: update to 3.6.0.

Upstream change:

mikutter 3.6.0

* World
 * Twitter functions are now implemented as a plugin
 * Service is no longer available, so the World plugin provides an equivalent
   of Service
* Spell
* Form DSL
 * generalized modules for settings etc. so make it possible to use it
   in Dialog etc.
 * photo select
  * select images
 * label
 * link (Model viewer)
* Dialog DSL/dialog method
 * universal interface for plugins to show a dialog box
 * no dependencies on Gtk
* Photo Model
 * preserve image URLs for multiple sizes and use a proper larger size
   one for requested image
* new setting in config for the maxinum number of tweets in timelines
* settings
 * tree structure in side menu by "settings" block
 * improve drawing speed for settings with many items
* appearance settings for PostBox and World Shifter
* requires Ruby 2.3 and later
* gems for mikutter project
 * use Diva gem
  * new gem derived from mikutter
  * replacement of Retriever, mikutter still provides Retriever compatible
    interfaces
 * Delayer Deferred 2
  * async/await