Issue 4 make extensible

[sulimmesh]

PR for making escalar more extensible for temporary ES5 support.

[codecov-io]

Codecov Report

Merging #7 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master     #7   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          27     27           
  Lines         609    613    +4     
  Branches       57     61    +4     
=====================================
+ Hits          609    613    +4

Impacted Files	Coverage Δ
...main/scala/com/workday/esclient/EsClusterOps.scala	100% <ø> (ø)	✅
.../main/scala/com/workday/esclient/EsSnapshots.scala	100% <ø> (ø)	✅
...scala/com/workday/esclient/actions/CatAction.scala	100% <ø> (ø)	✅
...in/scala/com/workday/esclient/EsIndexingMeta.scala	100% <ø> (ø)	✅
...n/scala/com/workday/esclient/EsScanAndScroll.scala	100% <100%> (ø)	✅
src/main/scala/com/workday/esclient/EsQuery.scala	100% <100%> (ø)	✅
...rc/main/scala/com/workday/esclient/JestUtils.scala	100% <100%> (ø)	✅
...rc/main/scala/com/workday/esclient/EsAliases.scala	100% <100%> (ø)	✅
...in/scala/com/workday/esclient/EsIndexingDocs.scala	100% <100%> (ø)	✅

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[bojdell]

I'd personally prefer to avoid naming things with Genericand instead add 1_7 or 5 in the class names for the version-specific implementations.

[bojdell]

FYI took a quick pass at addressing my comment here: https://github.com/Workday/escalar/tree/issue-4-bo-wip , although it's still a WIP. I'll commit/merge it onto this PR when it's ready

[sulimmesh]

Awesome, I'll have the afternoon free tmrw and Thursday to take a look as well.