Log Message:
Update mikutter to 3.4.0-alpha3.

Upstream changes:

#mikutter 3.4.0-alpha3

* allow selecting events on clicks of reply and tweet with comments
* wrong tweet region size of reply and tweet with comments in some case

#mikutter 3.4.0-alpha2

* change place of custom rake task
* update po translation files

#mikutter 3.4.0-alpha1

See "new functions of mikutter 3.4" for details.
http://mikutter.blogspot.jp/2016/04/mikutter-34.html
 * tweet tab
 * new in-reply-to format
 * open video URL using browser
 * drop Ruby 2.0 support
 * plugin dependency map
 * "about" window supports alpha releases