Updates

optionally install python client

- add influxdb_bind_hostname var (defaults to ansible_hostname )
- deal w/ config format changes

Fix collectd and opentsdb brackets

added brackets to collectd and opentsdb for compatibility with 0.13

Removed peer data purge from cluster-test.yml to avoid confusion (and accidental destruction of data).

Modified cluster purge logic slightly (due to extra/dirty data being kept in the WAL). Added sane, non-destructive defaults.

Added extra configuration flags for meta/clustering update. Changed default storage engine to tsm in preparation for the 0.10.0 release.

Modified clustering configuration slightly so that service is fully stopped when purging peer metadata.

Assure the influxdb_configuration_dir path exists before trying to write configuration file to it

Hard-coded hostname and port replaced with Ansible variables.