if no point indices provided in view kernel, visualize all points
Groups readers w/ readers, writers w/ writers
Fix cross-references
Port MortonOrder filter
rename drivers as io
rename drivers as io
catch up drivers->io rename to master
hammer NUMTHREADS in travis build to 1 to see if first build stops getting killed
try NUMTHREADS=2
Merge pull request #620 from PDAL/drivers-to-io

rename drivers as io
Merge pull request #630 from PDAL/move-morton-filter

Port MortonOrder filter