Bumped version to 1.6.0.

Sorry for having kept you waited so long.

Author: ksoichiro

Diff for: docs/reference/release-notes.md

@@ -1,5 +1,11 @@
 # Release notes
 
+* v1.6.0
+    * Added header view feature to `ObservableGridView` (#148).
+    * Added footer view feature to `ObservableGridView` (#183).
+    * Updated `recyclerview-v7` library version to 22.2.0.
+    * Fixed ViewPager swiping bug in `ObservableListView` (#185).
+    * Fixed NPE in `ObservableRecyclerView` (#149).
 * v1.5.2
     * Fix `ObservableGridView` to use first child of line in height calculation.
 * v1.5.1

Diff for: gradle.properties

@@ -1,4 +1,4 @@
-VERSION_NAME=1.6.0-SNAPSHOT
+VERSION_NAME=1.6.0
 SYNCED_VERSION_NAME=1.5.2
 GROUP=com.github.ksoichiro