upgrade to Datomic v0.7 branch

major upgrade to Datomisca (eliminates the DatomicData hierarchy, among many other things.)
minor: optimize use of collections in DatomiscaAutoSource

Datomic.transact now takes a TraversableOnce so we can make use of this an minimize the creation of intermediate data structures.
bump deps for Datomisca

move a little further along the development branch of Datomisca.
https://github.com/pellucidanalytics/datomisca/releases/tag/v0.7-alpha-7
https://github.com/pellucidanalytics/play-datomisca/releases/tag/v0.7-alpha-3
Merge pull request #33 from dwhjames/topic/datomisca-0.7

Upgrade to alpha release of Datomisca (v0.7 branch)