Upsert

* Enhancements

* Works on JRuby using bare-metal JDBC!
* Simplified.

* Bug fixes

* Fix filenames - they were updated on an apparently case-insensitive setup. Thanks ihough! (https://github.com/seamusabshere/upsert/pull/8)
* Deliberately drop MySQL procedures before creating them. Also thanks to ihough!

* Bug fixes

* Fix incorrect gem description

* Breaking changes (well, not really)

* Not using INSERT ... ON DUPLICATE KEY UPDATE for MySQL!

* Enhancements

* Replaced ON DUPLICATE KEY with a true merge function (procedure)
* Simplified code - buffering is no longer used anywhere
* Clarified documentation

* Bug fixes

* MySQL upserts won't fail if you have a multi-key selector and no multi-column UNIQUE index to cover them (https://github.com/seamusabshere/upsert/issues/6)

* Breaking changes (well, not really)

* "document" (as in the second argument to row) has been renamed to "setter"!

* Bug fixes

* If you say upsert({:name => 'Jerry', :color => 'red'}), make sure that it only affects rows really meeting those conditions
* Always sort selector and setter keys - i.e., column names - before doing anything with them
* Support PostgreSQL 9.1+
* Support MRI 1.8

* Enhancements

* Slightly faster benchmarks for SQlite3 and MySQL
* Slightly slower on PostgreSQL (probably because the merge function requires more arguments), but more accurate
* Slightly clearer code structure
* Use bind parameters instead of quoting for PostgreSQL and SQLite3.
* Provide Upsert.clear_database_functions(connection) (currently only for PostgreSQL)
* Don't subclass String for Upset::Binary... hopefully save some strcpy()s?

* Bug fixes

* Don't raise TooBig - rely on Mysql2 to complain about oversized packets

* Enhancements

* Re-use PostgreSQL merge functions across connections, even outside of batch mode. Huzzah!
* For MySQL, increase speed for one-off upserts by not checking packet size
* Allow configuring Upsert.logger. Defaults to Rails.logger or Logger.new($stderr). If you set env var UPSERT_DEBUG=true then it will set log level to debug.