issue-185: Fixed closestLiveHost method in CassandraConnector

Before that fix, the method used only the hosts which were considered up by the Java driver. However, under a heavy load, this information may not be very up-to-date and in some cases the set of live hosts visible by the Java driver is empty.
The fix comes from the recent changes in LocalNodeFirstLoadBalancing policy - the hosts which are considered down are not filtered out. Instead, they are attached to the tail of the sequence.

Fixes #185
#185 Remove some duplicate code from CassandraConnector and LocalNodeFirstLoadBalancingPolicy.
Merge branch 'b1.0' of https://github.com/datastax/spark-cassandra-connector into issue-185

Conflicts:
	CHANGES.txt
Merge pull request #186 from datastax/issue-185

issue-185: Fixed closestLiveHost method in CassandraConnector, Fixes #185