Merge pull request #4 from kbu1564/developer

issue #1, #2 처리 완료
#1 IDT의 시작주소를 담는부분에 0x00000000을 담아서 발생한 문제
#2 64MiB 메모리 체크 함수와 A20 기능 활성화 체크 함수의 분리
Merge pull request #7 from kbu1564/developer

issue #3 처리 완료
Merge pull request #11 from kbu1564/developer

issue #6, #8, #9, #10 처리 완료
Merge pull request #12 from kbu1564/developer

그래픽 모드 전환 작업중이던 코드가 합쳐져서 오작동 일으키는 문제 수정
Update README.md & Development environment is changed to linux.
Merge pull request #13 from kbu1564/developer

marge update README.md
Update README.md & Development environment is changed to linux.
Update README.md
update .gitignore
Merge branch 'master' into developer

Conflicts:
	.gitignore
	README.md
	helloos/Bootloader/loader.bin
	helloos/Image/loader.img
	helloos/Kernel/kernel.sys
	helloos/makefile