adding async method

[amed83]

I've added async method, and changed postTransaction end-point to "transactionCommit"
Closes #191

[codecov-io]

Codecov Report

Merging #197 into master will increase coverage by 1.22%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #197      +/-   ##
==========================================
+ Coverage   84.43%   85.65%   +1.22%     
==========================================
  Files          11       11              
  Lines         257      258       +1     
==========================================
+ Hits          217      221       +4     
+ Misses         40       37       -3

Impacted Files	Coverage Δ
src/connection.js	88.88% <0%> (-3.42%)	⬇️
src/baseRequest.js	79.31% <0%> (+6.89%)	⬆️
src/request.js	92.85% <0%> (+14.28%)	⬆️

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[future-is-present]

Good.
Please add docs and maybe some tests

[future-is-present]

Docs need to be updated

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@206e4ce). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #197   +/-   ##
=========================================
  Coverage          ?   86.82%           
=========================================
  Files             ?       11           
  Lines             ?      258           
  Branches          ?        0           
=========================================
  Hits              ?      224           
  Misses            ?       34           
  Partials          ?        0

Impacted Files	Coverage Δ
src/connection.js	100% <100%> (ø)

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[future-is-present]

@jernejpregelj can you review? :)