gdt: use a static GDT, so we don't have to create one in cpu::init()
Replaced the obsolete zero.rs with the actively developed rust-core.
vga: make COLS/ROWS public constants, so users of the vga module know x/y limits
io: no need to use ioval::zero() anymore in io::inport
implemented abort() in Rust
Rustic now sets up the x86 IDT and is therefore now able to handle CPU exceptions, as well as hardware IRQs.

A little spinner in the bottom right corner now ticks every second.
vga: return final offset from vga::write, move VGA cursor on write
mach: keyboard driver, writes keys are pressed to the screen including tabs and newlines. Shift works too!
resolving merge conflicts
Now that we use rust-core instead of zero.rs, fix IDT/KB/PIC.
Update README.md

Updated the readme to reflect the fact that we no longer just write text and loop forever.
Update README.md

Information about git submodules, updated qemu example, added links to other projects and info about IRC.