Support reply

* Abstract reply from `PostListActivity`.
* Abstract `AbsPostFragment` from `Loader`.
* Add reply menu to 'PostListPagerFragment`.
* Add TranslucentLightTheme and TranslucentDarkTheme.
* Replace the reply menu icon.
* Replace `Result` model (renamed from `Authority`) with `Reply` model.
Disable flip page menu when post only has one page
Show grey icon menu when disabled

* Add grey icon menu.
* Add selector to menu which could be disabled.
Tweak code
Bump to Gradle 2.2 and Gradle plugin 0.14.4

* Remove `gradleHome` setting