remove redundant mb_substitute_character line from bootstrap
Track latest submodules
Track unittest submodule for init_modules() support

The unittest module needs to call Kohana::init_modules()
once it registers the appropriate modules to build.
Update cache submodule to fix failing unittests

The cache module had been updated to 3.4/develop in a114c69 but
3.4/develop was not up to date with 3.3/develop.
Merge pull request #48 from kohana/3.4/enhancement/remove-redundant-mb_substitute_character-from-bootstrap

Remove redundant mb_substitute_character line from bootstrap