Beam 2.5.0 and some refactorings

[labianchin]

• sbt 1.2.0
• Refactorings to improve performance

[codecov-io]

Codecov Report

Merging #33 into master will decrease coverage by 0.09%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master      #33     +/-   ##
=========================================
- Coverage   88.93%   88.84%   -0.1%     
=========================================
  Files           7        7             
  Lines         235      233      -2     
  Branches       31       27      -4     
=========================================
- Hits          209      207      -2     
  Misses         26       26

Impacted Files	Coverage Δ
...c/main/scala/com/spotify/dbeam/MetricsHelper.scala	100% <100%> (ø)	⬆️
.../scala/com/spotify/dbeam/JdbcAvroConversions.scala	82.66% <100%> (-0.46%)	⬇️

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