Added support map queryresult groupby

[fmachado]

Updated README.md and CHANGELOG.md.
#343

[fmachado]

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@fmachado would you mind adding a Changelog entry and extended documentation ?

btw: thanks for this.
-- #345

No prob! Could you please check if the documentation is clear and what you expected?

[codecov-io]

Codecov Report

Merging #346 into master will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@## master #346 +/- ##
=========================================
Coverage 83.44% 83.44% Complexity 199 199 =========================================
Files 16 16 Lines 906 906 Branches 91 91 =========================================
Hits 756 756 Misses 107 107 Partials 43 43

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