Update reqs to get tox running

[ahopkins]

Looks like all of a sudden the requirements were killing builds. This was able to get things running again locally, but I think first priority after next release is a 100% overhaul of these and getting all versions up to date.

https://travis-ci.com/github/huge-success/sanic/jobs/464682171

[codecov]

Codecov Report

Merging #1986 (ea9cf36) into master (6515dde) will increase coverage by 0.37%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1986      +/-   ##
==========================================
+ Coverage   92.49%   92.87%   +0.37%     
==========================================
  Files          29       29              
  Lines        3198     3241      +43     
  Branches      566      566              
==========================================
+ Hits         2958     3010      +52     
+ Misses        162      156       -6     
+ Partials       78       75       -3     

Impacted Files	Coverage Δ
sanic/views.py	100.00% <0.00%> (ø)
sanic/blueprint_group.py	100.00% <0.00%> (ø)
sanic/response.py	98.71% <0.00%> (+0.01%)	⬆️
sanic/router.py	97.10% <0.00%> (+0.04%)	⬆️
sanic/request.py	99.23% <0.00%> (+0.04%)	⬆️
sanic/app.py	95.86% <0.00%> (+0.04%)	⬆️
sanic/errorpages.py	99.25% <0.00%> (+0.04%)	⬆️
sanic/worker.py	84.42% <0.00%> (+0.12%)	⬆️
sanic/testing.py	96.25% <0.00%> (+0.14%)	⬆️
sanic/server.py	82.17% <0.00%> (+1.72%)	⬆️

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