Code Review Request: TLS 1.3 Implementation

[Anthony Scarpino]

Here are questions I have about the code before I or someone makes a change:

ChangeCipherSpec.java
- 69 & 200:  Given this is legacy data on older version of TLS, is the 
exception better worded "Not supported"?  "yet" implies future additions.
- ChangeCipherSpec is removed in 1.3, why is there a T13 consumer ? 
Client/ServerHello are consuming these messages too, shouldn't their 
references be removed as well?


Below are some changes I will make:
Alert.java
- optimized imports.

Authenticator.java
- 271-2: Clarifying comments about byte array ordering.  Moved sequence 
number to the end
- 406: static declaration for the interface is redundant

ClientHandshakeContext:
- 3 spelling errors

Tony