update release date for R-package

update release date for R-package

v2.3.0 realese (microsoft#2138)

* Update DESCRIPTION

* bump minor version

2.2.3 release (microsoft#1987)

* Update DESCRIPTION

* Update DESCRIPTION

fix a bug in WeightedPercentile function.

update R's version (microsoft#1727)

new release (microsoft#1649)

* Update VERSION.txt

* Update DESCRIPTION

* Update .appveyor.yml

* Update .appveyor.yml

* Update DESCRIPTION

* Update VERSION.txt

* Update .appveyor.yml

* Update DESCRIPTION

* Update VERSION.txt

* Update DESCRIPTION

update version

update version in appveyor build

update version