Changing keyspace strategy

Changing the strategy of a keyspace from SimpleStrategy to NetworkTopologyStrategy.

A keyspace is created with a strategy. For development work, the SimpleStrategy class is acceptable. For production work, the NetworkTopologyStrategy class must be set. To change the strategy, two steps are required.

Procedure

Change the snitch to a network-aware setting.
Alter the keyspace properties using the ALTER KEYSPACE command. For example, the keyspace cycling set to SimpleStrategy is switched to NetworkTopologyStrategy.
```
ALTER KEYSPACE cycling 
WITH REPLICATION = {
      'class' : 'NetworkTopologyStrategy', 
      'DC1' : 3, 
      'DC2' : 2 };
```
Note: Datacenter names are case sensitive.