Implementation of BEP-14

[future-is-present]

Implement https://github.com/bigchaindb/BEPs/tree/master/14

[codecov-io]

Codecov Report

Merging #239 into master will increase coverage by 0.2%.
The diff coverage is 96.59%.

@@            Coverage Diff            @@
##           master     #239     +/-   ##
=========================================
+ Coverage   94.96%   95.16%   +0.2%     
=========================================
  Files          11       12      +1     
  Lines         258      310     +52     
=========================================
+ Hits          245      295     +50     
- Misses         13       15      +2

Impacted Files	Coverage Δ
src/transport.js	100% <100%> (ø)
src/connection.js	100% <100%> (ø)	⬆️
src/baseRequest.js	83.33% <86.66%> (-2.88%)	⬇️
src/request.js	96.96% <96.66%> (+4.11%)	⬆️

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