Squashed commit of the following:

commit 94b482a6eccb5ecccee4a845fc8099ad58fd5bcd
Author: ItsEddy <yukkcake@gmail.com>
Date:   Wed Nov 19 12:26:40 2014 +0800

    Make all demo have a same interface.

    Now use `make demo%` to make the binary.
    The flash command doesn't change.

commit 538017a90ee640c2b1ea8bd847fa5bd5cd6a62a7
Author: ItsEddy <yukkcake@gmail.com>
Date:   Wed Nov 19 11:40:07 2014 +0800

    Clean up unnecessary files

commit 5f4071317590a1391e81649391f5036df368c0ec
Author: ItsEddy <yukkcake@gmail.com>
Date:   Wed Nov 19 11:18:43 2014 +0800

    Clean up Makefile.

    Clean up output message, and adjust variable in an appropriate order.