Fixed fatal error: concurrent map writes

[solomkinmv]

I've replaced the map with the custom map which supports concurrent write operations. Sources of concurrent map based on this repository.

[marminthibaut]

Nice job!
Thx

[solomkinmv]

Something went wrong. I need to check.

Update: I had to change some test cases because of new data structure.

[codecov-io]

Current coverage is 72.43%

Merging #92 into develop will increase coverage by +2.39% as of df32884

@@            develop     #92   diff @@
=======================================
  Files             7       8     +1
  Stmts           404     439    +35
  Branches         25      28     +3
  Methods           0       0       
=======================================
+ Hit             283     318    +35
  Partial           4       4       
  Missed          117     117       

Review entire Coverage Diff as of df32884

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