Compact JSON representation

[pickfire]

Issue #, if available:

Description of changes: Compact JSON for Response, this removes unneeded whitespaces in response.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #958 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #958   +/-   ##
=======================================
  Coverage   95.52%   95.52%           
=======================================
  Files          27       27           
  Lines        4449     4449           
  Branches      558      558           
=======================================
  Hits         4250     4250           
  Misses        128      128           
  Partials       71       71

Impacted Files	Coverage Δ
chalice/app.py	96.75% <100%> (ø)	⬆️

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[joguSD]

I've confirmed this works when actually deployed.
With PR:

> curl $(chalice url)    
{"hello":"world"}%    

Current master:

> curl $(chalice url)  
{"hello": "world"}%

Considering this did break assertions we were making, I'm wondering if we should consider this a breaking change and make this configurable instead.