Gzip files, by serving w/ nginx not flask

[adelavega]

Addresses #908 by adding gzip to Nginx.

The problem was the wrong mimetype was issued for json files, and flask served the main index.html file, not nginx.

[codecov-commenter]

Codecov Report

Merging #925 (48e06f5) into master (284aea2) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #925      +/-   ##
==========================================
+ Coverage   83.14%   83.16%   +0.01%     
==========================================
  Files          62       62              
  Lines        3103     3100       -3     
==========================================
- Hits         2580     2578       -2     
+ Misses        523      522       -1     

Impacted Files	Coverage Δ
neuroscout/core.py	67.85% <ø> (+0.11%)	⬆️

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[cypress]

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Test summary

0 • 7 • 0 • 0

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Run details

Project	Neuroscout
Status	Failed
Commit	48e06f5
Started	May 4, 2021 10:02 PM
Ended	May 4, 2021 10:03 PM
Duration	00:51 💡
OS	Linux Ubuntu - 20.04
Browser	Electron 87

View run in Cypress Dashboard ➡️

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Failures

	analysis_builder.spec.js		1
1	Analysis Builder > analysis builder
	home_spec.js		6
1	The Home Page > successfully loads
2	The Home Page > navigation bar contents
3	The Home Page > splash page contents
4	The Home Page > test sign up button 1
5	The Home Page > test sign up button 2
6	The Home Page > test sign in button

---

This comment has been generated by cypress-bot as a result of this project's GitHub integration settings. You can manage this integration in this project's settings in the Cypress Dashboard

[cypress]

---

Test summary

0 • 7 • 0 • 0

---

Run details

Project	Neuroscout
Status	Failed
Commit	a822559 ℹ️
Started	May 4, 2021 10:03 PM
Ended	May 4, 2021 10:03 PM
Duration	00:46 💡
OS	Linux Ubuntu - 20.04
Browser	Electron 87

View run in Cypress Dashboard ➡️

---

Failures

	analysis_builder.spec.js		1
1	Analysis Builder > analysis builder
	home_spec.js		6
1	The Home Page > successfully loads
2	The Home Page > navigation bar contents
3	The Home Page > splash page contents
4	The Home Page > test sign up button 1
5	The Home Page > test sign up button 2
6	The Home Page > test sign in button

---

This comment has been generated by cypress-bot as a result of this project's GitHub integration settings. You can manage this integration in this project's settings in the Cypress Dashboard