gray-crawler: refactored MBR code into generic PT code
Merge pull request #25 from cmusatyalab/generalized-partition-handling

gray-crawler: refactored MBR code into generic PT code
gray-crawler: mbr code now properly uses SECTOR_SIZE constant
gray-crawler: fixed large memory leak in crawling code
Merge GPT with master. GPT build is currently broken for ARM. #14.