Merge pull request #3 from zhangdenghui/master

modify /tasks/task_1.md
Update task_1.md

modified task_1.md
better format
add task 2
update readme
add suggestion section for readme
image format
add link for task 2 explanation
Merge pull request #4 from pp2codexu/master

add xu's task summary
git simple tutorial
git simple tutorial
comment for my task#1
Update task_1.md
add my name
add my name for summary
Merge pull request #5 from hutsonlu/master

task#1 summary
update readme
better format
update summary for weizhicheng
Merge branch 'weizhicheng-patch-1'