Merge pull request #2 from akeeton/master

Add GitHub default client .gitattributes.
Run 'cargo new 6502emu --bin'
Add some stuff.
Merge branch 'from-scratch' of https://github.com/akeeton/6502-rs into from-scratch
Add add_with_carry().
Merge branch 'master' into from-scratch
Try to split into modules.
Fix modules.
Add new() methods and get main() running.
Add a BitFlag enum for the Status registers, replacing u8s.
Rename the Status register sign to negative.
Add Cargo.lock to .gitignore.
Add Cargo.lock to .gitignore.  Remove the .gitignore created by Cargo.
Add Cargo.lock to .gitignore.
git rm Cargo.lock
Remove redundant entry in .gitignore.
Add unit test for add_with_carry().  Fix carrying logic.
Integrate AddressDiff.
Integrate IRQ.
Integrate AddressingMode.