SEP-10 v3.1: updated python stellar sdk, lock files, and SEP-10 function calls

[JakeUrban]

resolves #377

[codecov-io]

Codecov Report

Merging #378 (9039df1) into master (8a062f5) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #378      +/-   ##
==========================================
+ Coverage   69.60%   69.61%   +0.01%     
==========================================
  Files          44       44              
  Lines        2790     2791       +1     
==========================================
+ Hits         1942     1943       +1     
  Misses        848      848              

Impacted Files	Coverage Δ
polaris/polaris/sep10/views.py	74.41% <100.00%> (+0.30%)	⬆️

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