refine statements

refine statement

fixe date typo

fix typo in wrappers.md and update status in README.md

finish picker.md

change the title name of picker.md

change picker.md link and title

refine diagram

re-structure the content of conn2.md and picker.md

merge conn2.md and picker.md

change the content directory

ready for 'pick a connection' chapter

add picker.md

update diagram

add diagram