Minor changes.

Change a Q&A info according to new photo layer implementation.
Minor changes.

Quick fix for last commit.
New implementation for photo layer support.

This partially fixes Issue #6.
Currently only working for comment button in the first-shown photo layer. Those after it may not work since our Mutation Observer only listens at newly added nodes, but Tencent sometimes hides and then re-shows the layer using css.
This commit introduces Mutation Observer, which may slow down the system. Needs continuing observations.

Also, add a missing `document.createTextNode()` for inserting text emoticons.