Add client support for auth_tag when using AES GCM

[orip]

[codecov-io]

Codecov Report

Merging #627 into master will decrease coverage by 0.00%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #627      +/-   ##
==========================================
- Coverage   96.59%   96.58%   -0.01%     
==========================================
  Files          79       79              
  Lines       16893    16894       +1     
==========================================
  Hits        16317    16317              
- Misses        576      577       +1     

Impacted Files	Coverage Δ
kmip/services/kmip_client.py	71.34% <100.00%> (+0.03%)	:arrow_up:
kmip/__init__.py	94.11% <0.00%> (-5.89%)	:arrow_down:

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[orip]

Pinging @PeterHamilton - are you interested in a change like this?