Fixes #15:
1. Remove some very horrible code, a little work toward merging multiple groupings but it's too difficult for this ticket, fixes #157
2. Fix bug in grouping and disable useless double grouping but coalesce group projects is totally broken
3. Fix bugs in inlining projects into group

fix double grouping bug, enable complicated test case
Merge branch 'master' of github.com:jdegoes/slamengine into ready/15
Merge pull request #168 from jdegoes/ready/15

Support flat grouping, fixes #15
Fixes #15:
1. Remove some very horrible code, a little work toward merging multiple groupings but it's too difficult for this ticket, fixes #157
2. Fix bug in grouping and disable useless double grouping but coalesce group projects is totally broken
3. Fix bugs in inlining projects into group

fix double grouping bug, enable complicated test case
Merge branch 'master' of github.com:slamdata/slamengine