remove callback

does not pass a callback function.

https://github.com/shibukawa/oktavia/issues/21#issuecomment-40689310
> Callback strategy was changed from 0.5.
export `search` and `getPage`

`search` and `getPage` been used in `oktavia-jquery-ui.js`
Merge pull request #22 from tuchida/work-non-webworker

Do not work non-Web Worker version