Merge pull request #29 from industrial-sloth/custom-rdds

Custom rdds: image to series conversion via block slicing
Pass user_data option
Merge pull request #30 from industrial-sloth/custom-rdds

Custom rdds: s3 reader
Explicit specification of key number
Simplified parsing buffer
Swapped order of loading parameters and normalizing file pattern
Increase kryo buffer for EC2
Loading bug fixes
- Fixed concatenation error
- Added TODO about lazy first