added and test snapshots of new query
add tests for observation with query.snapshot
replicated code related to **document changes** from cursor
added basic chaneges
added limit_only tests
added complete sort and limit tests
added method
added observer - but not tested
added observer and tests
added snapshot callback support
added empty removed to make sure, db connection is established
added invalidator.initiateQuery()
added new query engine support to invalidator
accepting an optional callback while adding an observer
fixed fields filtering issue which loaded before loading the collection
moved Meteor.bindEnvironment in overserver to the cursor
resolve tests for cursor/observations
move _selectorMatcher() cursor to query
server collection write op callback fires after the invalidations initiated
updated latency compensation tests
tests updated to be make it less prone for failure