Test ci (#50)

* renamed a few test files.
tested the dropna function

* indexer tests

* subtraction

* Subtract, divide, and equals

* DataFrame operators - equality

* added pop test

* Sample test added.
Added support for sample with replace.

* Create ubuntu-dotnet.yml

* Update ubuntu-dotnet.yml

* Remove reference to TensorFlow.NET

* Update PandasConsole.indexers.cs

* ubuntu, windows, and macos ci

* fixing macos file 1

* mac os dependencies

* macox test

* another test

* more tweaks

* fixing up the macos build

* more ci work

* removed tensorflow from test package

* disable the macos test for now

Author: brettwebst