Some partially ported functions
Allow passing write options
Failing test :/
Try to add aggregations
Fix incomplete test
Handle case of no data folded
Properly open and close leveldb dbs

They were being created per group, not per test, then caused errors 
referencing the group db when trying to iterate. Closing helped at first,
but they should each use a new DB
Examples!
Merge pull request #1 from philipcristiano/online-algs

Online algs