bump xgboost version to 0.82

[tanmaykm]

because 0.80 fails to compile, at least on Linux with the following error:

│ g++ -c -DDMLC_LOG_CUSTOMIZE=1 -std=c++11 -Wall -Wno-unknown-pragmas -Iinclude   -Idmlc-core/include -Irabit/include -I/include -O3 -funroll-loops -fPIC -DDISABLE_OPENMP src/data/data.cc -o build/data/data.o
│ In file included from src/data/data.cc:10:0:
│ src/data/./simple_dmatrix.h:19:7: error: looser throw specifier for 'virtual xgboost::data::SimpleDMatrix::~SimpleDMatrix() noexcept (false)'
│  class SimpleDMatrix : public DMatrix {
│        ^
│ In file included from src/data/data.cc:5:0:
│ include/xgboost/data.h:347:11: error:   overriding 'virtual xgboost::DMatrix::~DMatrix() noexcept'
│    virtual ~DMatrix() = default;
│            ^
│ Makefile:141: recipe for target 'build/data/data.o' failed
│ make: *** [build/data/data.o] Error 1