First swipe at MapReduce evaluation.
Add support for PureTask to insert a set of documents.
Add FoldLeftTask.

For sequential composition of tasks.
[minor] Formatting.
remove dummy type param
fix count(*)
first whack at a failing test for schema lost during merge
Move MapReduce actions inside the companion object.
updte tests
fix one issue with making arrays / objects from pipelined expressions
code cleanup, refactor functionality of pipeline schema
Merge branch 'master' of github.com:slamdata/slamengine into merging
Merge pull request #92 from mossprescott/between

remove dummy type param
Merge pull request #94 from sellout/13-mongodb-equi-joins

A few more pieces around the edges of Mongo joins.
work in progress
Merge branch 'merging' of github.com:mossprescott/slamengine-1 into merging
patch up in case schema is Init
fix broken tests
Merge pull request #96 from jdegoes/merging

Revamp merging algorithm to preserve structure on both sides. Fixes #96, closes #96.