Compare Java and Scala BigDecimal with tolerance

[nightscape]

I noticed that for java.math.BigDecimal no tolerance comparison is done in DataFrameSuite.approxEquals and scala.math.BigDecimal is missing completely.
Is there a reason for that?
If there isn't I would add corresponding test cases along with this change.

[codecov-io]

Codecov Report

Merging #213 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #213   +/-   ##
=======================================
  Coverage   86.36%   86.36%           
=======================================
  Files          46       46           
  Lines        1005     1005           
  Branches       89       86    -3     
=======================================
  Hits          868      868           
  Misses        116      116           
  Partials       21       21

Flag	Coverage Δ
#python	85.87% <ø> (ø)	⬆️
#scala	70.76% <0%> (-0.27%)	⬇️

Impacted Files	Coverage Δ
...holdenkarau/spark/testing/DataFrameSuiteBase.scala	0% <0%> (ø)	⬆️

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[nightscape]

I added tests for the 2.0 branch, but didn't find an existing 1.3 tests where I could add the BigDecimal case.
Also the stuff that codacy complains about is because I used the existing code style in the 1.3 case.
Are you OK with leaving it as is?

[holdenk]

So if the relative tolerance for bigdecimal support only exists in 2+ we should only test it in 2+, but the style issues are fine.

[holdenk]

If you've got the time to move the new test code from 1.3 to 2+ that would be great, but if not let me know and I can do that part.

[holdenk]

Gentle follow up. If I don't here back I'll assume your busy and do the last fix :)

[nightscape]

Hi @holdenk,
my second child was born a few days ago and I won't get to do much coding in the next time 😉
If you could take over the last fix that would be great!

Thanks a lot!

[holdenk]

Ok I'll take this on and try and fix it after Spark 2.3 goes out so we can have it with that release :)

[holdenk]

Also congratulations!!!!!!!!!!!!!!!!!!