Fix typo
Merge pull request #489 from kenjis/patch-1

Fix typo
reorganized the download page, added a link for the future 1.5. related #490
clarified the contribution procedure. related #490
bumped the copyright to 2013
documented $_write_connection
documented master/slave setup for ORM
fixed incorrect syntax on related() with conditions
Documented ORM related() 'join_on' option
Update download links