Allow wildcard at end of deref_expr.

Fixes issue #39.
Failing tests for qualified wildcards.
Fix compilation of qualified wildcards.
first whack at a failing test for schema lost during merge
Update constructors in test.
updte tests
Merge branch 'master' of github.com:slamdata/slamengine into merging
Add a test for deeply-nested select *.
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.
Check for required Java version when starting sbt.
Merge pull request #98 from sellout/minor-fixes

Check for required Java version when starting sbt.
Add a note to the Readme that building requires Java 7.
pull ExprOp out of pipeline.scala

Conflicts:
	src/main/scala/slamdata/engine/physical/mongodb/pipeline.scala
break out all merging-related code to merge.scala
(not including the merge() methods, yet)
pull out all merging-related code to merge.scala
Merge pull request #99 from sellout/minor-fixes

Add a note to the Readme that building requires Java 7.