Revising API & embedding examples

- Updated docblocks, & added examples
- Fixed `array.split()`, & `Observable.unhook()`
- Defaulting second parameter of `client.request()` to `GET`
- Removed `client.script()`, `client.size()`, & `client.stylesheet()`
- Added `addEventListener()`, `removeEventListener()`, & `removeListener()` facades on prototypes for consistent APIs
- Created `DataGrid.add()`, `DataGrid.remove()`, & `DataGrid.update()` as a simple abstraction of the underlying `DataStore`
- Created `DataList.add()`, `DataList.remove()`, & `DataList.update()` as a simple abstraction of the underlying `DataStore`
- Exposed `keigai.util.repeat()`