Adding a pre-test check that looks for java files in the test/scala d…

[yfarjoun]

…irectory and for scala files anywhere else (and fails if it finds either of these)

Description

Please explain the changes you made here.
Explain the motivation for making this change. What existing problem does the pull request solve?

Checklist

• Code compiles correctly
• New tests covering changes and new functionality
• All tests passing
• Extended the README / documentation, if necessary
• Is not backward compatible (breaks binary or source compatibility)

[lbergelson]

I think we usually start task names with lowercase

[droazen]

"and java files there" -> "and java files in the scala test dir" (description is a little confusing as-is)

[droazen]

👍 merge after addressing comments

[codecov-io]

Codecov Report

Merging #857 into master will increase coverage by 0.022%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##              master      #857       +/-   ##
===============================================
+ Coverage     64.904%   64.926%   +0.022%     
- Complexity      7198      7210       +12     
===============================================
  Files            527       527               
  Lines          31784     31821       +37     
  Branches        5425      5433        +8     
===============================================
+ Hits           20629     20660       +31     
- Misses          9018      9021        +3     
- Partials        2137      2140        +3

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/htsjdk/samtools/fastq/FastqReader.java	74.775% <0%> (-6.306%)	32% <0%> (+8%)
...main/java/htsjdk/samtools/SAMRecordSetBuilder.java	89.113% <0%> (+0.806%)	64% <0%> (+2%)	⬆️
...samtools/util/AsyncBlockCompressedInputStream.java	76% <0%> (+4%)	13% <0%> (+1%)	⬆️
...sjdk/samtools/util/Md5CalculatingOutputStream.java	79.487% <0%> (+7.692%)	9% <0%> (+1%)	⬆️

[yfarjoun]

verbal 👍 at review party.