add range data structures
CON-171: Fix bug that made phantom reads possible in transactions

This commit adds real time notifications for range
version changes, which prevents phantom reads within
transactions.

Conflicts:
	concourse-server/src/main/java/org/cinchapi/concourse/server/storage/Engine.java
	concourse-server/src/main/java/org/cinchapi/concourse/server/storage/Transaction.java