Have api_settings respond to settings_changed

[dakotahawkins]

This is identical to what happens for rest_framework.settings.api_settings.

It should allow (for example) overriding the expiration deltas for a unit test.

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@0a0bd40). Click here to learn what that means. The diff coverage is 83.33%.

@@            Coverage Diff            @@
##             master     #458   +/-   ##
=========================================
  Coverage          ?   90.22%           
=========================================
  Files             ?       12           
  Lines             ?      829           
  Branches          ?       31           
=========================================
  Hits              ?      748           
  Misses            ?       67           
  Partials          ?       14

Flag	Coverage Δ
#codecov	90.22% <83.33%> (?)
#dj110	86.97% <83.33%> (?)
#dj111	86.97% <83.33%> (?)
#dj18	89.38% <83.33%> (?)
#dj19	89.38% <83.33%> (?)
#drf33	89.38% <83.33%> (?)
#drf34	90.22% <83.33%> (?)
#drf35	89.86% <83.33%> (?)
#drf36	89.86% <83.33%> (?)
#py27	90.22% <83.33%> (?)
#py34	89.86% <83.33%> (?)
#py35	86.97% <83.33%> (?)
#py36	86.97% <83.33%> (?)

Impacted Files	Coverage Δ
rest_framework_jwt/settings.py	88.88% <83.33%> (ø)

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[dakotahawkins]

Eh, this doesn't seem like it's going to work anytime soon, so closing this for now.