Handle constant cols in DRF2
Merge branch 'master' of github.com:0xdata/h2o
Fixed bug in sum light parse. When adding more columns, the min/max were filled with zeros, which is correct except for the last column (the one currently being added) off we're at the first line (in which case, zero might never occur in this column).
Add tiny mnist dataset for debugging

Use MemoryManager for some arrays
Fast cutout for histogram scoring
Merge branch 'master' of github.com:0xdata/h2o