Distributed indexes return to Thinking Sphinx.

They're useful as a catch-all index for a model, especially useful in situations with multiple indices for a single model.

At this point in time, they are there but mostly unused, unless you search directly on them.
Opting for a little more conciseness.
Revert "Gather database connection details from ActiveRecord."

This reverts commit 117fad9b425d6514e2810303cce25a139bc60d60.

Conflicts:
	lib/thinking_sphinx/active_record/sql_source.rb
Custom database settings can be set in the index definition.

Instead of connecting to a database (though if you're using multiple databases and the schemas are different, that may be required), you can just use set_database in the index definition.

It either takes a hash of database settings with the same keys that Rails expects, or a symbol or string indicating a specific environment (and use the matching configuration from config/database.yml).
Avoid concurrent indexing via temporary files.
Don't filter out delta records for the core source.
Reset delta column after core indexing has completed.

Instead of doing it before. This ensures that delta indices continue to work as expected while core indices are being processed. See #522.
Merge branch 'feature/distributed' into develop
Merge branch 'feature/multidb' into develop
Merge branch 'feature/index-guard' into develop
Suspended delta blocks can also flag delta records as deleted.
One deletion class instead of two.
Allow passing of options to delta processors via :delta_options
Fix ThinkingSphinx::ActiveRecord::SQLSource#delta_processor spec to pass with delta_options
Added a new test in ThinkingSphinx::ActiveRecord::SQLSource#delta_processor spec to test delta_options