tests for conditional ddl

for CASSANDRA-7604
Merge pull request #71 from riptano/ddl_conditional

tests for conditional ddl
fix conditional ddl assertions and restrict one test to 2.1+
Merge branch 'master' of https://github.com/riptano/cassandra-dtest
Remove trailing whitespace
fix whitespace
Removed 1.1 upgrade testing
Merge branch 'master' into python-driver

Conflicts:
	upgrade_through_versions_test.py
	user_types.py