Initial push to add cassandra adapter using 'cql'.
1.  Added #execute_dui to cassandra adapter
2.  Overwrite the complex_expression_sql_append
Remove rescue clause from complex_expression_sql_append
1.  Added hash mapping rules
2.  Started on mapping arrays
Moved custom insert methods into /shared/cassandra.rb folder.  Started on keyspace and table generation methods.
Changed filtering expression to not use parenthesis during literal string condition
Added method to drop keyspace in Sequel::Database
Don't wrap tables and columsn in quotes, and don't set a default keyspace by default.
Added support for insert sql into cassandra
Removed extraneous binding.pry
converts all array members and hash keys/values to string instead of preventing them from saving.
Merge branch 'adapters/redshift_2' into adapter/cassandra
- cassandra.rb adapter change due to cql-rb upgrade to 2.0.3: use default_consistency and pass through options w/o manipulation, don't manually set read/write_consistency
- add Sequel::Cassandra::DatabaseMethods.native_paginate to support C* 2.0 native pagination, which is very different from the pagination in the Sequel gem.
Set up a new branch to serve Redshift, but not Cassandra