* Fix#3545: XGDMatrixCreateFromCSCEx silently discards empty trailing rows
Description: The bug is triggered when
1. The data matrix has empty rows at the bottom. More precisely, the rows
`n-k+1`, `n-k+2`, ..., `n` of the matrix have missing values in all
dimensions (`n` number of instances, `k` number of trailing rows)
2. The data matrix is given as Compressed Sparse Column (CSC) format.
Diagnosis: When the CSC matrix is converted to Compressed Sparse Row (CSR)
format (this is common format used for DMatrix), the trailing empty rows
are silently ignored. More specifically, the row pointer (`offset`) of the
newly created CSR matrix does not take account of these rows.
Fix: Modify the row pointer.
* Add regression test
* [R] make sure things work for a single split model; fixes#2191
* [R] add option use_int_id to xgb.model.dt.tree
* [R] add example of exporting tree plot to a file
* [R] set save_period = NULL as default in xgboost() to be the same as in xgb.train; fixes#2182
* [R] it's a good practice after CRAN releases to bump up package version in dev
* [R] allow xgb.DMatrix construction from integer dense matrices
* [R] xgb.DMatrix: silent parameter; improve documentation
* [R] xgb.model.dt.tree code style changes
* [R] update NEWS with parameter changes
* [R] code safety & style; handle non-strict matrix and inherited classes of input and model; fixes#2242
* [R] change to x.y.z.p R-package versioning scheme and set version to 0.6.4.3
* [R] add an R package versioning section to the contributors guide
* [R] R-package/README.md: clean up the redundant old installation instructions, link the contributors guide
* [R] xgb.save must work when handle in nil but raw exists
* [R] print.xgb.Booster should still print other info when handle is nil
* [R] rename internal function xgb.Booster to xgb.Booster.handle to make its intent clear
* [R] rename xgb.Booster.check to xgb.Booster.complete and make it visible; more docs
* [R] storing evaluation_log should depend only on watchlist, not on verbose
* [R] reduce the excessive chattiness of unit tests
* [R] only disable some tests in windows when it's not 64-bit
* [R] clean-up xgb.DMatrix
* [R] test xgb.DMatrix loading from libsvm text file
* [R] store feature_names in xgb.Booster, use them from utility functions
* [R] remove non-functional co-occurence computation from xgb.importance
* [R] verbose=0 is enough without a callback
* [R] added forgotten xgb.Booster.complete.Rd; cran check fixes
* [R] update installation instructions
