Optimize the way of parsing memo in TransactionResponse.

[overcat]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 76.35%. Comparing base (bc6a69d) to head (7d65706).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #582      +/-   ##
============================================
+ Coverage     76.10%   76.35%   +0.25%     
+ Complexity     1129     1128       -1     
============================================
  Files           220      219       -1     
  Lines          5085     5042      -43     
  Branches        464      461       -3     
============================================
- Hits           3870     3850      -20     
+ Misses          917      897      -20     
+ Partials        298      295       -3     

Files	Coverage Δ
.../java/org/stellar/sdk/responses/GsonSingleton.java	97.87% <ø> (-0.05%)	⬇️
...g/stellar/sdk/responses/OperationDeserializer.java	82.50% <ø> (-0.43%)	⬇️
...va/org/stellar/sdk/responses/PageDeserializer.java	100.00% <ø> (ø)
...org/stellar/sdk/responses/TransactionResponse.java	80.95% <81.81%> (+14.28%)	⬆️

... and 2 files with indirect coverage changes