Fix github vulnerabilities

[adelavega]

• Fixes SQLAlchemy and Jinja vulnerabilities
• Simplifies Docker file for faster building
• Fixes issue with installing Node

[codecov-io]

Codecov Report

Merging #546 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #546   +/-   ##
=======================================
  Coverage   84.03%   84.03%           
=======================================
  Files          38       38           
  Lines        1616     1616           
=======================================
  Hits         1358     1358           
  Misses        258      258

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