Rename from drucker to rekcurd

[keigohtr]

What is this PR for?

Rename project naming from drucker to rekcurd.

[codecov-io]

Codecov Report

Merging #18 into master will not change coverage.
The diff coverage is 98.21%.

@@           Coverage Diff           @@
##           master      #18   +/-   ##
=======================================
  Coverage   87.37%   87.37%           
=======================================
  Files           8        8           
  Lines         293      293           
=======================================
  Hits          256      256           
  Misses         37       37

Impacted Files	Coverage Δ
rekcurd_client/_project.py	100% <ø> (ø)
rekcurd_client/logger/logger_interface.py	70.58% <ø> (ø)
rekcurd_client/logger/__init__.py	100% <ø> (ø)
rekcurd_client/_version.py	100% <ø> (ø)
rekcurd_client/__init__.py	100% <100%> (ø)
rekcurd_client/logger/logger_jsonlogger.py	75% <100%> (ø)
rekcurd_client/logger/logger_fluent.py	46.15% <100%> (ø)
rekcurd_client/rekcurd_worker_client.py	95.16% <98.03%> (ø)

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[yuki-mt]

LGTM