title: Unable to create more than two table using sync_table() in cqlengine
body: <p>I have the following class in python and am using cqlengine as object mapper for cassandra DB,</p>
  
  <pre><code>class Company(Model):
      id = columns.Integer(index=True, primary_key=True)
      company_name = columns.Text(required=False)
      created_at = columns.DateTime(default=datetime.now)
  
  class Social(Model):
      id = columns.Integer(index=True, primary_key=True)
      name = columns.Text(required=False)
  
  class UserCompany(Model):
      id = columns.Integer(index=True, primary_key=True)
      user_id = columns.Integer(required=True)
      company_id = columns.Integer(required=True)
  
  array_of_tables=[UserCompany, Company, Social]
      for table in array_of_tables:
          sync_table(table)
  </code></pre>
  
  <p>Issue: Am not able to create more than two table in cassandra while executing the code. </p>
  
  <p>Erorr message:</p>
  
  <pre><code>  File "test.py", line 109, in &lt;module&gt;
      create_tables()
    File "test.py", line 68, in create_tables
      sync_table(table)
    File "/usr/lib64/python2.6/site-packages/cassandra/cqlengine/management.py", line 259, in sync_table
      execute(qs)
    File "/usr/lib64/python2.6/site-packages/cassandra/cqlengine/connection.py", line 171, in execute
      result = session.execute(query, params, timeout=timeout)
    File "cassandra/cluster.py", line 1602, in cassandra.cluster.Session.execute (cassandra/cluster.c:27334)
    File "cassandra/cluster.py", line 3347, in cassandra.cluster.ResponseFuture.result (cassandra/cluster.c:65206)
  cassandra.InvalidRequest: code=2200 [Invalid query] message="Cannot create secondary index on partition key column id"
  </code></pre>
  
  <p>Need you help in resolving this issue.</p>