new remap transform to change namespaces

[jipperinbham]

fixes #341

• CHANGELOG.md updated
• README.md updated

[codecov]

Codecov Report

Merging #400 into master will decrease coverage by 0.09%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #400     +/-   ##
=========================================
- Coverage   84.15%   84.05%   -0.1%     
=========================================
  Files          59       60      +1     
  Lines        4102     4115     +13     
=========================================
+ Hits         3452     3459      +7     
- Misses        482      486      +4     
- Partials      168      170      +2

Impacted Files	Coverage Δ
message/message.go	100% <100%> (ø)	⬆️
function/remap/remap.go	100% <100%> (ø)
adaptor/postgres/tailer.go	78.21% <0%> (-2.98%)	⬇️

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