Avoid endless loops on errors.
Better, more specific error handling.

Mysql2::Errors get translated to ThinkingSphinx::SphinxErrors (or subclasses).
Don't expect a colon after error types.
Shift namespaced model documentation.
Updating HISTORY with recent changes.
Better handling of associations within polymorphic assocaitions.
Noting MySQL support is required, and why mysql2 is necessary.
Support new JDBC conf style for TS v3.
Merge pull request #440 from kstevens715/jdbc_new_syntax_support_v3

Support new JDBC conf style for TS v3.
Updating gemfiles for Travis.