Use new std::io module

[robo9k]

This is a work-in-progress to port the code to the new std::io module.

Note that std::io itself contains the following warning:

NOTE: This module is very much a work in progress and is under active development. At this time it is still recommended to use the old_io module while the details of this module shake out.

As such, do not merge until the dust has settled ✋

[jakerr]

Looking good so far 😄 Thank you for your proactivity in starting this!

[robo9k]

Note that the Travis cargo build fails due to a rustc ICE in Piston/image, see https://travis-ci.org/chip8-rust/chip8-ui/builds/50792473#L2697
I did not investigate this any further or reported in anywhere upstream, but I don't think it's a problem with this pull request's code changes.

Edit: So this ICE is already a few days old, see rust-lang/rust#21756 (comment)

[robo9k]

Rebased onto aa5d470. Now this fails as expected, since chip8-rust/chip8-vm#2 has not been merged after the split.

[robo9k]

Even though I've successfully merged the chip8_vm part (though no new crate version yet), this pull request here fails to build due to a problem with rust-sdl2, so we're a little stuck.

[robo9k]

Okay, the issue with rust-sdl2 is fixed by 9a3a31a. I get a new nasty error about

SDL not built with haptic (force feedback) support

however USE=haptic emerge libsdl2 fixed that for now (might be a bug in Gentoo's stable media-libs/libsdl2).