Update to glutin 0.22.0-alpha5, remove wasm_stub (#260)

Update from glutin 0.21.x fork to glutin 0.22.0-alpha5 and corresponding
compatible version of winit. This removes our custom temporary wasm_stub
branches, back to mainline glutin and winit, and is a step towards WebAssembly
compatibility, most importantly merging the game loop and event loops as
required by winit _which now supports wasm_. Not yet functional on the web
because other web dependencies have to be added, see #171 and #34, but native
functionality is preserved.

* Update for 0.22 glutin API changes:

* Move game logic into event loop, run() replacing poll_events()

* Specify fullscreen Borderless mode

* Pass generic parameter of Event through handle_window_event
* hidpi_factor() replaces get_hidpi_factor()
* with_inner_size() replaces with_dimensions()
* No longer need to unwrap() LogicalSize
* set_cursor_grab/visible() replaces grab/hide_cursor()

* Fix modifiers deprecated warnings by destructuring only event fields we use, ignoring the rest with '..'

* Remove unnecessary mutability from events_loop

* Listen for ModifiersChanged event, fixing deprecated modifiers field

* Change to stdweb for web backend, replacing web-sys

* Pin to glutin =0.22.0-alpha5 and winit =0.20.0-alpha6

Author: iceiix