window: remove doc.go
window: add new doc.go
window: link to azul3d.org not godoc.org
window: fix some spelling issues
window: add the initial workings of the communicative main loop

See issues #39 and #40.
window: mention that windows must be closed for the app to exit.
window: space a code section out
window: implement the Num function
window: better Precision documentation
window: clarify New's dependency on MainLoop running.
window: initial implementation of New
window: sync New and Run documentation better
window: implement Run using New and MainLoop
window: prefer blank line for code sections in comments.
First working build of multi-window & exposed main loop.
example: add gfx_multiwindow example (opens two windows).
Merge pull request #49 from azul3d/v2-window

window: add multiple-window support and expose main loop.