docs: Clarify how to use a client with InfluxDB 1.8

[bednar]

• CHANGELOG.md updated
• Rebased/mergeable
• Tests pass
• Sign CLA (if not already signed)

[codecov-io]

Codecov Report

Merging #35 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #35   +/-   ##
=======================================
  Coverage   99.31%   99.31%           
=======================================
  Files          12       12           
  Lines         582      582           
=======================================
  Hits          578      578           
  Misses          4        4           

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