Move secrets from Travis into repo

[c-w]

See #463

[codecov-commenter]

Codecov Report

Merging #465 into master will decrease coverage by 0.25%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #465      +/-   ##
==========================================
- Coverage   76.46%   76.21%   -0.26%     
==========================================
  Files          45       45              
  Lines        2766     2766              
==========================================
- Hits         2115     2108       -7     
- Misses        651      658       +7     

Impacted Files	Coverage Δ
opwen_email_server/services/sendgrid.py	94.40% <0.00%> (-5.60%)	⬇️

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