Use 'text' formatter for 'ascii' values

patch by Mikhail Stepura; reviewed by Brandon Williams for CASSANDRA-7407
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	pylib/cqlshlib/formatting.py