started schema-constraints
added schema-constraints
some adjustments
some adjustments
Merge remote-tracking branch 'upstream/master' into schemaconstraints

Conflicts:
	py2neo/neo4j.py
Merge remote-tracking branch 'upstream/master' into schemaconstraints

Conflicts:
	py2neo/neo4j.py
Merge remote-tracking branch 'upstream/master' into schemaconstraints
Merge pull request #277 from umeier/schemaconstraints

Schemaconstraints
Entity -> _Entity
Merge branch 'master' into feature/bindable

Conflicts:
	py2neo/neo4j.py