unify formate, clean some path variable
move primary makefile to the root of dir
not finished
fix some path error
change target name, let making .bin and .elf be a rule
move object file list to board.mk
make obj list with src list
objs will rebuild when any related .h file changes
Do not track *.d files
fix travis ci srcipt
Merge pull request #158 from UrsusPilot/makefile_dev

Makefile improvement