fix: updated and fixed changelog md

CHANGELOG.md

-# 1.6.0-dev
+# 1.6.2
+- Now AR.js emits events when a marker is found and lost, when using aframe's `<a-marker>` [merged PR](https://github.com/jeromeetienne/AR.js/pull/303)
+- configured travis CI
+- minor bug fixes
 
-nothing yet...
+# 1.6.1
+
+# 1.6.0
 
 # 1.5.5