replaces kohana/database as a dependency (eg for kohana/orm)
update composer.json:

- replace tabs with spaces
- remove version (use git tags)
- require PHP 5.4 or greater
Add MySQLi Database driver (refs #3898)
Oops, fix transparent extension (refs #3898)
classes -> src, update docblock
remove empty extensions
add phpunit to dev deps
remove mysql, it is deprecated
test mysqli connection