* bump scala to 2.12 which requires java 8 and also newer flink and akka
* put scala version in artifactId
* fix appveyor
* fix for scaladoc issue that looks like https://github.com/scala/bug/issues/10509
* fix ci_build
* update versions in generate_pom.py
* fix generate_pom.py
* apache does not have a download for spark 2.4.3 distro using scala 2.12 yet, so for now i use a tgz i put on s3
* Upload spark-2.4.3-bin-scala2.12-hadoop2.7.tgz to our own S3
* Update Dockerfile.jvm_cross
* Update Dockerfile.jvm_cross
* Fix test_gpu_coordinate.
* Use `gpu_coord_descent` in test.
* Reduce number of running rounds.
* Remove nthread.
* Use githubusercontent for r-appveyor.
* Use githubusercontent in travis r tests.
* Expand histogram memory dynamically to prevent large allocations for large tree depths (e.g. > 15)
* Remove GPU memory allocation messages. These are misleading as a large number of allocations are now dynamic.
* Fix appveyor R test
* Fail GPU CI after test failure
* Fix GPU linear tests
* Reduced number of GPU tests to speed up CI
* Remove static allocations of device memory
* Resolve illegal memory access for updater_fast_hist.cc
* Fix broken r tests dependency
* Update python install documentation for GPU
* [R] fix finding R.exe with cmake on WIN when it is in PATH
* [R] appveyor config for R package
* [R] wrap the lines to make R check happier
* [R] install only binary dep-packages in appveyor
* [R] for MSVC appveyor, also build a binary for R package and keep as an artifact
* for MinGW, drop the 'lib' prefix from shared library name
* fix defines for 'g++ 4.8 or higher' to include g++ >= 5
* fix compile warnings
* [Appveyor] add MinGW with python; remove redundant jobs
* [Appveyor] also do python build for one of msvc jobs
* [jvm-packages] Fixed compilation on Windows
* [jvm-packages] Build the JNI bindings on Appveyor
* [jvm-packages] Build & test on OS X
* [jvm-packages] Re-applied the CMake build changes reverted by #2395
* Fixed Appveyor JVM build
* Muted Maven on Travis
* Don't link with libawt
* "linux2"->"linux"
Python2.x and 3.X use slightly different values for ``sys.platform``.
