Merge pull request #2 from ottbot/1.2-use-cql2-in-specs

Use CQL 2.0.0 for specs if using cassandra 1.2 or above.
Precalculate a map of column names -> column indices

This allows us to avoid using Array#index to map names to indices, which
requires N**2 comparisons between column names to fully hydrate a row.
Performance improvements are considerable for large result rows.
Remove #column_index helper; use #column_indices to check for int name
Fix column_family_spec to not check for column.id attribute now absent in cassandra 1.2
Prevent thrift 0.9 from being used until more thorough tests can be run
Bump version to 1.1.5
Get applicable specs working with Cassandra 1.2/CQL3

* Define constant CQL_VERSION in specs, read from environment and
  defaults to 2.0.0
* Use this constant to filter specs which have a :cql_version option
  defined
* Set :cql_version to 2.0.0 for specs that deal with comparators and
  sparse columns
* Create spec helper modules to deal with different setup behavior for
  CQL2 and CQL3, particularly introspecting for the existence of a
  column family
* In some specs, needed to explicitly define columns which could be
  lazily created by insert in CQL2
Support for reading collection columns in results

Define CassandraCQL::Collections::List, CassandraCQL::Collections::Set,
and CassandraCQL::Collections::Map, which implement a ::cast class
method that takes a block to cast each individual element. The return
types are Array, Set, and Hash respectively.
Set the consistency level used for CQL3 queries
Change the consistency level used for a connection
Use a different consistency level within a block