[ci] hotfixes (#2132)

* Update Features.rst

* Update .appveyor.yml

* Update test_windows.ps1

* Update test_windows.ps1

* Update .appveyor.yml

* Update test_windows.ps1

* Update .appveyor.yml

.appveyor.yml

-version: 2.2.4.{build}
+version: 2.2.4.{build}
 
 image: Visual Studio 2015
 platform: x64
@@ -31,6 +31,7 @@ install:
   - conda update -q -y conda
   - conda create -q -y -n test-env python=%PYTHON_VERSION% matplotlib nose numpy pandas psutil pytest python-graphviz scikit-learn scipy
   - activate test-env
+  - set PATH=%CONDA_PREFIX%\Library\bin\graphviz;%PATH%  # temp graphviz hotfix
 
 build_script:
   - cd %APPVEYOR_BUILD_FOLDER%\python-package

.ci/test_windows.ps1

@@ -6,6 +6,8 @@ function Check-Output {
   }
 }
 
+$env:PATH += ";$env:CONDA_PREFIX\Library\bin\graphviz"  # temp graphviz hotfix
+
 if ($env:TASK -eq "regular") {
   mkdir $env:BUILD_SOURCESDIRECTORY/build; cd $env:BUILD_SOURCESDIRECTORY/build
   cmake -DCMAKE_GENERATOR_PLATFORM=x64 .. ; cmake --build . --target ALL_BUILD --config Release ; Check-Output $?

docs/Features.rst

@@ -283,7 +283,7 @@ References
 
 .. _On Grouping for Maximum Homogeneity: https://www.researchgate.net/publication/242580910_On_Grouping_for_Maximum_Homogeneity
 
-.. _Optimization of collective communication operations in MPICH: http://wwwi10.lrr.in.tum.de/~gerndt/home/Teaching/HPCSeminar/mpich_multi_coll.pdf
+.. _Optimization of collective communication operations in MPICH: https://www.mcs.anl.gov/~thakur/papers/ijhpca-coll.pdf
 
 .. _A Communication-Efficient Parallel Algorithm for Decision Tree: http://papers.nips.cc/paper/6381-a-communication-efficient-parallel-algorithm-for-decision-tree