Add timestamp separator in message view using extra DecoratedChatItem

[zwang]

Just show an example of how to accomplish user case mentioned in #9 according to @diegosanchezr 's suggestion

See screenshot below. The timestamp separator is at the top

[codecov-io]

Current coverage is 62.40%

Merging #58 into dev will not affect coverage as of 5cb720c

@@             dev    #58   diff @@
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  Files         57     57       
  Stmts       2857   2857       
  Branches       0      0       
  Methods        0      0       
===================================
  Hit         1783   1783       
  Partial        0      0       
  Missed      1074   1074       

Review entire Coverage Diff as of 5cb720c

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[zwang]

Also resolved potential self.dynamicType issue found earlier.

[diegosanchezr]

Thank you very much @zwang!

[zwang]

Thank you! @diegosanchezr 👍

I think we can also close #9 now. :)