Allow pid file to be read by mere mortals.

Patch by Michael Shuler, reviewed by brandonwilliams for CASSANDRA-7851
Merge branch 'cassandra-2.0' into cassandra-2.1
Fix yaml snitch reconnect trick

Patch by Holger Bornträger, reviewed by brandonwilliams for CASSANDRA-7912
Merge branch 'cassandra-2.0' into cassandra-2.1
deprecate yaml snitch
Fix CHANGES.txt
Dont try to set repairedAt on old sstables

Patch by marcuse; reviewed by jbellis for CASSANDRA-7913
Add human readable option to nodetool outputs.

Patch by Michael Nelson, reviewed by brandonwilliams for CASSANDRA-5433
Don't try to shutdown client servers if they don't exist.

Patch by Steve Nelson, reviewed by brandonwilliams for CASSANDRA-7889
Merge branch 'cassandra-2.0' into cassandra-2.1